Fab Fragment?
Rationale:
C: Binds antigen. The Fab fragment is the part of an antibody that specifically binds to antigens, playing a crucial role in the immune response by recognizing and attaching to foreign molecules.
A: Is produced by pepsin treatment. Pepsin treatment does not yield Fab fragments; instead, it cleaves antibodies into fragments that do not retain the specific binding function of Fab.
B: Is produced by separation of heavy and light chains. While separation of chains occurs in antibody structure, the Fab fragment specifically refers to the binding region derived from the combination of these chains.
D: Lacks light chains. The Fab fragment consists of both heavy and light chains, integral for its function in antigen binding, thus it cannot exist without light chains.
Anaphylaxis can be triggered by cross-linking of IgE receptors on...?
Rationale:
Anaphylaxis can be triggered by cross-linking of IgE receptors on mast cells. Mast cells, when activated through IgE receptor cross-linking, release histamines and other mediators, leading to the severe symptoms associated with anaphylaxis. This process highlights their crucial role in immediate hypersensitivity reactions.
A: monocytes Monocytes are not directly involved in the immediate hypersensitivity mechanism; their role primarily involves phagocytosis and immune response regulation rather than mediating anaphylaxis.
B: B-cells B-cells primarily function in antibody production and do not directly participate in the rapid release of inflammatory mediators characteristic of anaphylactic reactions.
C: eosinophils Eosinophils are associated with chronic allergic responses and parasitic infections, not with the immediate release of mediators that precipitate anaphylaxis triggered by IgE cross-linking.
Matching: Complement deficiency - Fatal meningococcal infection in males
Rationale:
Complement deficiency - Fatal meningococcal infection in males is associated with Properdin. This protein plays a crucial role in the complement pathway, enhancing the immune response against Neisseria meningitidis, thus preventing severe infections.
A: C5, 6, 7, 8, 9 are part of the membrane attack complex but do not initiate the immune response needed for combating meningococcal infections effectively.
B: C3 is vital for opsonization and inflammation; however, deficiencies in C3 alone do not specifically correlate with fatal meningococcal infections in males.
C: C1q is involved in the classical complement pathway but primarily targets different pathogens and does not provide direct protection against meningococcal bacteria like Properdin does.
Which of the following is not a prominent feature of Wiskott-Aldrich syndrome?
Rationale:
Leukopenia is not a prominent feature of Wiskott-Aldrich syndrome. This condition is characterized primarily by atopic dermatitis, thrombocytopenia, and recurrent infections with encapsulated bacteria, while leukopenia does not typically present in patients with this syndrome.
A: Atopic dermatitis A hallmark of Wiskott-Aldrich syndrome, atopic dermatitis manifests as chronic skin inflammation, significantly impacting the quality of life for affected individuals.
B: Thrombocytopenia This condition features a reduced platelet count, leading to increased bleeding tendencies, making it a significant clinical aspect of Wiskott-Aldrich syndrome.
C: Recurrent infections with encapsulated bacteria Individuals with this syndrome frequently experience infections from encapsulated bacteria due to compromised immune function, highlighting a critical health concern.
A 15-month-old male child presented with thrombocytopenic purpura, atopic dermatitis, and recurrent infections caused by cytomegalovirus and P.jiroveci. Immunoglobulin assay revealed elevated IgE and IgA with decreased IgM levels. Of the following, the MOST likely diagnosis is
Rationale:
A 15-month-old male child likely has Wiskott-Aldrich syndrome. This diagnosis aligns with his symptoms of thrombocytopenic purpura, atopic dermatitis, and recurrent infections, alongside the immunoglobulin profile indicating low IgM and elevated IgE and IgA.
B: X-linked lymphoproliferative syndromes This condition primarily presents with severe immunodeficiency and susceptibility to viral infections, but does not typically feature atopic dermatitis or thrombocytopenic purpura.
C: Nijmegen breakage syndrome Characterized by immunodeficiencies and microcephaly, this syndrome does not present with the classic triad of symptoms seen in this patient, including the specific immunoglobulin profile.
D: Omenn syndrome This condition features a severe combined immunodeficiency with eosinophilia and skin rashes, but it lacks the thrombocytopenic purpura and specific immunoglobulin abnormalities found in this child.
which of the following cells will be the last cell to perform its function in skin pathogen invasion
Rationale:
Naïve CD8 Lymphocytes will be the last cells to perform their function in skin pathogen invasion. They require initial activation and differentiation into effector cells, which typically occurs after other immune responses have already begun.
A: Natural killer cells respond quickly to infected cells, providing an early defense against pathogens before other adaptive immune cells are activated.
C: Intraepithelial Lymphocytes are positioned strategically within epithelial tissues to act swiftly against pathogens, offering immediate protection upon invasion.
D: Macrophages are among the first responders to infection, actively engulfing pathogens and signaling for further immune activation, thus functioning earlier in the immune response.
All of the following are actions of IL-1 EXCEPT
Rationale:
D: IL-1 is primarily involved in promoting inflammation, which includes increasing blood vessel permeability rather than decreasing it. Its actions focus on enhancing immune responses and facilitating the movement of white blood cells to affected areas.
A: Proliferation of WBCs stimulates the immune response, a key role of IL-1, which encourages the growth and activation of white blood cells in response to pathogens.
B: Migration of WBCs to the site of inflammation is a crucial function of IL-1, as it signals immune cells to move toward areas requiring immune action and repair.
C: Inflammatory response describes IL-1's role in initiating and sustaining the body's defense against infection, making it an essential mediator in the overall inflammatory process.
Which one of the following leukocytes is considered a 'granulocyte'?
Rationale:
B: Neutrophil is classified as a granulocyte due to its distinct granules in the cytoplasm, which contain enzymes and substances vital for fighting infections. This characteristic, along with its role in the immune response, solidifies its classification as a granulocyte within the leukocyte family.
A: Macrophage lacks granules in its cytoplasm, classifying it instead as an agranulocyte. It primarily functions in phagocytosis and antigen presentation, rather than being categorized as a granulocyte.
C: Dendritic cell is also an agranulocyte, characterized by its role in antigen processing and presentation. It does not possess the granules that define granulocytes like neutrophils.
D: Natural killer cell is classified as an agranulocyte and specializes in targeting virus-infected and tumor cells. Its lack of granules excludes it from the granulocyte category.
The classical and alternative pathways meet at complement component:
Rationale:
C3. The classical and alternative pathways converge at complement component C3, which plays a pivotal role in the complement system, facilitating opsonization and activation of various immune responses.
B: C4 The component C4 is involved in the classical pathway but does not serve as the convergence point for both pathways.
C: C4b While C4b is a fragment of C4 and plays a role in the classical pathway, it does not represent the meeting point for both pathways.
D: C5 C5 is a component downstream of C3 and is involved in the terminal pathway, not the convergence of the classical and alternative pathways.
A CD3pos cell that secretes perforin and granzyme is a:
Rationale:
Cytotoxic T cell.
Cytotoxic T cells are characterized by their ability to secrete perforin and granzyme, which are crucial for inducing apoptosis in infected or cancerous cells. These effector functions are essential for immune defense against intracellular pathogens and tumor surveillance, highlighting the critical role of CD3pos cytotoxic T cells in the adaptive immune response.
A: (γδ) T cell. These T cells possess distinct receptors and primarily respond to non-peptide antigens, lacking the perforin and granzyme secretion characteristic of cytotoxic T cells.
B: Helper T cell. Helper T cells primarily assist other immune cells by releasing cytokines, focusing on orchestrating immune responses rather than directly killing infected or malignant cells.
D: Regulatory T cell. Regulatory T cells play a vital role in maintaining immune tolerance and preventing autoimmune responses, without the cytotoxic functions associated with perforin and granzyme secretion.
A 4.5-year-old boy presented with history of recurrent attack of secretary otitis media and purulent nasal discharge, Haemophilus influenza revealed by culture of ear discharge, on physical examination there is no tonsillar tissue and no palpable lymph nodes. Of the following, the MOST appropriate test to confirm the diagnosis is
Rationale:
D: antibodies to antigens of routine immunizations. This test is essential for confirming the diagnosis of specific antibody deficiency, especially considering the recurrent infections and the absence of tonsillar tissue in the child.
A: flow cytometry. This test assesses immune cell populations but does not directly evaluate antibody responses or confirm the specific diagnosis related to recurrent infections.
B: IgA concentration. While measuring IgA levels can provide information about the immune system, it does not specifically confirm the presence of antibodies to vaccine-preventable diseases.
C: isohemagglutinins titer. This test evaluates blood group antibodies but is not relevant for diagnosing infections or evaluating the immune response to vaccination in this clinical scenario.
A 15-year-old boy with rheumatoid arthritis, on quinine for 6 months, presented with fever, aphthous stomatitis, and fatigue for the last 5 days. His absolute neutrophil count (ANC) was 700/μL. The MOST next appropriate therapeutic measure to be done when quinine withdrawal fails to improve neutropenia is
Rationale:
Administration of recombinant human granulocyte colony-stimulating factor is the most appropriate therapeutic measure. This treatment stimulates the bone marrow to produce more neutrophils, addressing the patient's neutropenia effectively.
A: Administration of IVIG would not directly address the underlying issue of neutropenia, as it primarily provides antibodies rather than stimulating neutrophil production in the bone marrow.
B: Aggressive use of antibiotics focuses on treating infections rather than resolving the neutropenia, which requires a specific intervention to enhance neutrophil production in the patient.
C: Transplantation of hematopoietic stem cells is a drastic measure typically reserved for severe cases and not the first-line approach for addressing drug-induced neutropenia.
Which of the following is a messenger that mediates the connection between the innate and adaptive immune systems?
Rationale:
D: Cytokines serve as crucial signaling molecules that facilitate communication between innate and adaptive immune systems, coordinating responses and promoting interactions among various immune cells to enhance the overall immune response.
A: Complement components primarily function in the innate immune response, helping to opsonize pathogens and activate inflammation, but they do not mediate connections between the innate and adaptive systems.
B: Vaccines stimulate adaptive immunity by exposing the immune system to antigens, yet they do not act as mediators between the innate and adaptive immune systems in real-time responses.
C: T and B lymphocytes are key players in the adaptive immune system, but they do not serve as messengers; rather, they respond to signals from other immune components.
Macrophages
Rationale:
Macrophages perform phagocytosis and bacteriocidal mechanisms, as well as antigen presentation. This multifaceted role enables them to effectively eliminate pathogens and present antigens to T cells, crucial for adaptive immunity.
B: Lysis of some virally infected cells focuses solely on a specific action of immune cells, not encompassing the broader functions of macrophages, which include phagocytosis and antigen presentation.
C: Killing parasites highlights a particular function but overlooks the essential roles of macrophages in phagocytosis and the presentation of antigens, which are fundamental to their immune response capabilities.
D: Phagocytosis and bacteriocidal mechanisms describe only part of macrophage activity, omitting antigen presentation, a vital aspect of their function in initiating and regulating immune responses.
A cluster of genes that encode proteins
Rationale:
A cluster of genes that encode proteins is the Major histocompatibility complex (MHC). MHC consists of a group of genes that play a crucial role in the immune response by presenting peptide fragments to T cells, thereby influencing the body's ability to recognize foreign antigens and initiate an immune response.
A: B cell receptor (BCR) This refers to a specific receptor on B cells, not a gene cluster, and primarily functions in recognizing antigens rather than encoding proteins.
B: T cell receptor (TCR) This pertains to a specific protein complex found on T cells, which recognizes antigens presented by MHC molecules and does not represent a gene cluster itself.
D: None of the above This option suggests that no choices are correct, whereas MHC accurately describes a gene cluster responsible for encoding proteins essential for immune function.
The aim of monoclonal antibody production is to produce cells that only secrete immunoglobulin directed against the antigen used in immunization. Which of the following hybridoma production steps is NOT correct?
Rationale:
Cells are cultured in a selective medium allowing only fused cells to survive, which is a critical aspect of hybridoma technology. However, the statement implies non-fused cells can also survive, which is inaccurate and misrepresents the selection process required for successful hybridoma production.
A: Immunize a mouse with antigen of choice then remove the spleen when the mouse is making an antibody response. This step accurately describes the initial phase of generating an immune response necessary for hybridoma production.
B: Fuse the immune spleen cells with a myeloma tumor cell. This fusion step is essential, as it combines antibody-producing cells with immortal tumor cells to create hybridomas capable of continuous antibody production.
D: Cells are grown in individual culture plate wells, and culture supernatants from wells contain growing hybrid cells that are screened for presence of desired antibody by an enzyme-linked immunosorbent assay (ELISA). This procedure is standard practice for identifying hybridomas that produce the specific antibody of interest.
Penicillin can form a hapten-carrier conjugate with a self-protein that can then act as an immunogen and generate an immunoglobulin antibody, and can cross-react with a number of other antibiotics. This can complicate the treatment of bacterial infections in these patients because they are unable to take the antibiotics necessary to combat the infection.
Rationale:
C: Penicillin can form a hapten-carrier conjugate with self-proteins, leading to the production of IgE antibodies. This process can trigger allergic reactions, complicating the treatment of bacterial infections in affected patients.
A: IgA primarily functions in mucosal immunity and does not typically mediate allergic responses associated with drug interactions, making it irrelevant in the context of penicillin-induced complications.
B: IgD's role in the immune system is mainly as a receptor on B cells and does not contribute to the allergic reactions or complications arising from penicillin exposure.
D: The option "None of the above" fails to acknowledge that IgE is indeed involved in the allergic response to penicillin, directly linking it to the complications in treatment.
If alternative processing uses the second polyadenylation site, then what type of heavy chain mRNA is derived?
Rationale:
C: δ (delta)
Alternative processing utilizing the second polyadenylation site leads to the generation of delta heavy chain mRNA. This specific modification is crucial for producing distinct immunoglobulin classes in B cells.
A: α (alpha) Alternative processing does not yield alpha heavy chain mRNA; this type is produced through different polyadenylation mechanisms that do not involve the second site.
B: γ (gamma) Gamma heavy chain mRNA arises from specific processing at other polyadenylation sites, which are not activated during the alternative processing involving the second site.
D: μ (mu) The mu heavy chain mRNA is generated through a distinct pathway and does not correlate with the use of the second polyadenylation site.
A TCR complex is comprised of the TCR, CD3 molecules, and which of the following CD3 chains?
Rationale:
A TCR complex is comprised of the TCR, CD3 molecules, and zeta (ζ) chains (two chains). The zeta chains play a crucial role in signaling within the T-cell receptor complex, facilitating the activation of T-cells upon antigen recognition, thereby ensuring an effective immune response.
A: Delta (δ) chain does not form part of the TCR complex; it is primarily involved in the structure of certain T-cell receptors, not CD3 signaling.
B: Gamma (γ) chain is associated with some TCRs but does not constitute the essential signaling components within the CD3 complex required for T-cell activation.
C: Epsilon (ε) chains (two chains) are part of the CD3 complex but are not exclusively sufficient for the complete TCR signaling function, as zeta chains are also essential.
Evidence is accumulating showing that polymorphism in the MHC may be advantageous. Homozygosity at HLA class I has been shown to be a(n) with respect to HIV/AIDS. Similarly, there is evidence that homozygosity at HLA class II the risk of hepatitis B virus infection persisting.
Rationale:
Homozygosity at HLA class I has been shown to be a disadvantage with respect to HIV/AIDS. Similarly, homozygosity at HLA class II increases the risk of hepatitis B virus infection persisting, suggesting that genetic diversity is crucial for effective immune responses.
A: Advantage; Homozygosity does not provide an advantage, as studies indicate it actually hampers immune response effectiveness against HIV/AIDS, which is essential for controlling the virus.
B: Advantage; While polymorphism may offer some benefits, the evidence clearly links homozygosity to increased risks, notably indicating that it is detrimental rather than advantageous in the context of these infections.
C: Disadvantage; Although homozygosity is indeed a disadvantage, the explanation fails to address the specific context of HIV/AIDS, which emphasizes the unique impact of HLA class I on immune response.
The transporter associated with antigen presentation (TAP) the peptides to traverse the membrane bilayer of the endoplasmic reticulum and bind in the empty peptide-binding groove of nascent MHC molecules being synthesized in the endoplasmic reticulum.
Rationale:
TAP permits Class I peptides to traverse the membrane bilayer of the endoplasmic reticulum. This process is essential for loading peptides onto nascent MHC Class I molecules, facilitating effective antigen presentation.
B: Permits; Class II. Class II molecules present extracellular antigens and are synthesized in a different pathway, not requiring TAP for peptide loading in the endoplasmic reticulum.
C: Does not allow; Class I. TAP is crucial for Class I molecules, enabling them to receive peptides from the cytosol, thus facilitating effective immune responses against intracellular pathogens.
D: Does not allow; Class II. Class II molecules operate independently of TAP, utilizing a separate mechanism for peptide loading from endosomal compartments rather than the endoplasmic reticulum.
Phagocytose, bacteriocidal activity, ADCC
Rationale:
Neutrophils exhibit phagocytosis, bactericidal activity, and antibody-dependent cellular cytotoxicity (ADCC). These functions are essential for the innate immune response, allowing neutrophils to effectively eliminate pathogens and contribute to inflammation.
A: Natural Killer (NK) cells Primarily engage in recognizing and destroying infected or cancerous cells rather than performing phagocytosis, which is a key function of neutrophils in immune defense.
C: Basophils Mainly participate in allergic responses and releasing histamine, lacking the primary roles of phagocytosis and bactericidal activity that neutrophils fulfill during pathogen invasion.
D: T-cytotoxic cells Focus on killing infected cells via specific recognition and cytotoxic mechanisms, diverging from the broader phagocytic and bactericidal functions characteristic of neutrophils.
Which of the following locations has cell that transport the antigens by transcytosis into sub-epithelial tissues (e.g. lamina propria) where they encounter lymphocytes?
Rationale:
Peyer's patches (gut-associated lymphoid tissue, GALT) are specialized structures that facilitate the transcytosis of antigens into sub-epithelial tissues, allowing for interaction with lymphocytes crucial for immune responses.
A: Tonsils (nasopharyngeal-associated lymphoid tissue, NALT) primarily function in trapping pathogens from the air and food, but they do not specialize in transcytosis of antigens into deeper tissues.
B: Adenoids (nasopharyngeal-associated lymphoid tissue, NALT) serve to capture airborne antigens, however, they lack the specific architecture and function for efficient transcytosis into sub-epithelial areas.
D: Axilla (lymph node center) does not transport antigens through transcytosis; instead, it filters lymph and is involved in immune responses rather than antigen transport into epithelial tissues.
Tolerance refers to the ability of B cells to:
Rationale:
Tolerance refers to the ability of B cells to tolerate self antigens. This concept is crucial for maintaining immune homeostasis and preventing autoimmune reactions, allowing B cells to function properly without attacking the body's own tissues.
A: Tolerate T cells. This option misunderstands the relationship; B cells primarily focus on recognizing antigens, while T cells have distinct yet complementary roles in immune responses.
B: Tolerate other B cells. B cells do not require tolerance towards their own kind, as their interactions are primarily collaborative; thus, this option misrepresents the essence of tolerance.
D: Tolerate foreign antigens. While B cells interact with foreign antigens, tolerance specifically refers to self-antigens, emphasizing the necessity to avoid immune reactions against the body’s own components.
The γδ T cell acts as a part of the first line of defense, recognizing microbial invaders. They appear to recognize commonly occurring microbial pathogens. Where can γδ T cells be found?
Rationale:
γδ T cells are found in the skin and gut mucosa. These locations provide essential barriers against microbial pathogens, allowing γδ T cells to efficiently identify and respond to infections at critical entry points.
A: Liver and kidney. These organs primarily focus on filtration and metabolic processes, lacking the specialized immune surveillance characteristics associated with γδ T cell activity against microbial threats.
B: Bone marrow and spleen. While these sites are crucial for hematopoiesis and adaptive immunity, they do not serve as primary locations for γδ T cell action against pathogens.
D: Respiratory tract and bone marrow. Although the respiratory tract contains immune cells, bone marrow serves mainly as a production site rather than an active frontline defense for γδ T cells.
Antiapoptotic molecules are encoded by the death-inhibiting family of bcl genes.
Rationale:
Antiapoptotic molecules are encoded by the death-inhibiting family of bcl genes. This statement is accurate as bcl genes play a critical role in regulating cell survival by preventing apoptosis, thereby contributing to cellular longevity and homeostasis.
B: FALSE This statement contradicts established biological principles, as bcl genes are specifically known to inhibit apoptotic pathways, highlighting their essential function in promoting cell survival rather than death.
To prevent inadvertent complement activation, eight inhibitors exist. Which of the following is an inhibitor preventing activation of C2 and C4, and prevents C3 activation by the alternative pathway?
Rationale:
C1 inhibitor. The C1 inhibitor specifically targets the classical pathway, preventing the activation of C2 and C4 while also inhibiting C3 activation through the alternative pathway, ensuring regulatory balance.
B: C2 inhibitor. This option suggests a focus solely on C2, lacking the broader impact on C4 and C3 activation that the C1 inhibitor provides.
C: C3 inhibitor. While it may seem relevant, this option does not address the upstream inhibition of C2 and C4, which is essential in this context.
D: C4 inhibitor. This choice limits its action to C4 alone, neglecting the critical role of C1 in preventing C2 activation and the broader implications for C3.
Enhance diapedesis and stimulate TH2 responses
Rationale:
Enhance diapedesis and stimulate TH2 responses. Cytokines, particularly IL-4, play a crucial role in promoting diapedesis, the movement of immune cells, and driving TH2 immune responses essential for combating parasites and allergens.
A: Trypase & Chemotrypsin. These proteases primarily function in the breakdown of proteins and do not directly influence the enhancement of diapedesis or the stimulation of TH2 responses.
B: Histamine. While histamine is involved in inflammatory responses, it does not specifically enhance diapedesis or stimulate TH2 responses like IL-4 does within the immune system.
D: Cytokines/TNF. TNF is primarily associated with pro-inflammatory responses and does not specifically promote the TH2 responses or enhance diapedesis as effectively as IL-4.
Immunostimulatory complexes (ISCOMS) can be used for mucosal vaccines and induce widespread mucosal immunity in the gut and respiratory tract. They are the one way that response can be promoted.
Rationale:
Cytotoxic T cell. Cytotoxic T cells play a crucial role in the immune response by directly targeting and eliminating infected or cancerous cells, thereby promoting widespread mucosal immunity in various tissues.
A: B cell. B cells primarily focus on antibody production and do not directly eliminate infected cells, making them less effective in inducing immediate mucosal immunity compared to cytotoxic T cells.
B: Helper T cell. Helper T cells support other immune cells but do not directly kill infected cells. Their primary function is to coordinate the immune response rather than induce mucosal immunity directly.
D: Macrophage. Macrophages are important for phagocytosis and antigen presentation, yet they do not directly mediate the cytotoxic response necessary for inducing widespread mucosal immunity.
A patient is being seen for recurrent infections. However, the patient does not seem to think anything special of these infections and there has been no previous diagnosis other than the infections. Lab work reveals abnormalities with hypochlorous acid and H2O2 conversion. Which of the following is the most likely?
Rationale:
Myeloperoxidase deficiency. This condition is characterized by recurrent infections due to impaired microbial killing, specifically linked to the patient's lab results showing issues with hypochlorous acid and hydrogen peroxide conversion, confirming myeloperoxidase's role in the immune response.
A: Ataxia telangiectasia. This genetic disorder involves immune dysfunction and neurological issues, not specifically tied to the lab findings of hypochlorous acid and H2O2 conversion deficits.
B: Wiskott-Aldrich syndrome (WAS). This syndrome combines eczema, thrombocytopenia, and immunodeficiency, but the specific lab abnormalities presented do not align with the characteristics of WAS.
C: Hereditary angioedema. Primarily causes recurrent swelling episodes due to complement deficiencies, unrelated to the patient's recurrent infections and the noted lab abnormalities in microbial killing.
Fab Fragment?
Rationale:
C: Binds antigen. The Fab fragment is a portion of an antibody that specifically recognizes and binds to antigens, facilitating the immune response by targeting foreign substances for destruction.
A: Is produced by pepsin treatment. While pepsin can cleave antibodies into fragments, the Fab fragment's defining characteristic is its antigen-binding capability, not its production method.
B: Is produced by separation of heavy and light chains. This choice confuses the process of antibody assembly with the function of the Fab fragment, which centers on binding to the antigen rather than its formation.
D: Lacks light chains. The Fab fragment consists of one heavy chain and one light chain, making this option misleading; lacking light chains does not describe the functional role of the Fab structure.
Anaphylaxis can be triggered by cross-linking of IgE receptors on...?
Rationale:
Anaphylaxis can be triggered by cross-linking of IgE receptors on mast cells. Mast cells, when activated by cross-linking, release histamines and other mediators, leading to severe allergic reactions and symptoms associated with anaphylaxis.
A: monocytes Monocytes do not play a direct role in anaphylaxis, as they are primarily involved in immune response and phagocytosis, not in IgE receptor cross-linking.
B: B-cells B-cells are responsible for antibody production and immune memory, but they do not directly mediate the anaphylactic response through IgE receptor cross-linking on their surface.
C: eosinophils Eosinophils primarily respond to parasitic infections and allergic responses, but they do not initiate anaphylaxis through IgE receptor cross-linking like mast cells do in this context.
Matching: Complement deficiency - Fatal meningococcal infection in males
Rationale:
Complement deficiency - Fatal meningococcal infection in males is associated with Properdin. Properdin plays a critical role in the alternative pathway of complement activation, which is essential for fighting against meningococcal infections effectively.
A: C5, 6, 7, 8, 9 These components are part of the terminal complement pathway, primarily involved in forming the membrane attack complex, not specifically linked to the initial defense against meningococcal infections.
B: C3 C3 is crucial for opsonization and inflammation; however, individuals deficient in Properdin are particularly vulnerable to meningococcal infections, indicating a distinct role of Properdin in this scenario.
C: C1q C1q is part of the classical complement pathway, which primarily activates in response to antibodies, thus not directly correlating with fatal meningococcal infections in males linked to Properdin deficiency.
Which of the following is not a prominent feature of Wiskott-Aldrich syndrome?
Rationale:
Leukopenia is not a prominent feature of Wiskott-Aldrich syndrome. The syndrome primarily manifests with atopic dermatitis, thrombocytopenia, and recurrent infections due to impaired immune response, but leukopenia is not typically observed in affected individuals.
A: Atopic dermatitis A key characteristic of Wiskott-Aldrich syndrome, atopic dermatitis presents as skin rashes and inflammation, significantly contributing to the syndrome's overall clinical picture.
B: Thrombocytopenia This condition, marked by low platelet counts, is a defining feature of Wiskott-Aldrich syndrome and leads to increased bleeding tendencies in affected patients.
C: Recurrent infections with encapsulated bacteria Patients face increased susceptibility to infections, particularly from encapsulated bacteria, due to compromised immune function associated with Wiskott-Aldrich syndrome, making this a hallmark symptom.
A 15-month-old male child presented with thrombocytopenic purpura, atopic dermatitis, and recurrent infections caused by cytomegalovirus and P.jiroveci. Immunoglobulin assay revealed elevated IgE and IgA with decreased IgM levels. Of the following, the MOST likely diagnosis is
Rationale:
A: Wiskott-Aldrich syndrome is the most likely diagnosis for this child, as it presents with thrombocytopenic purpura, eczema, and recurrent infections, alongside the specific immunoglobulin profile observed.
B: X-linked lymphoproliferative syndromes primarily lead to severe immunodeficiency and lymphoproliferation without the characteristic eczema or thrombocytopenia, making it less fitting for this child's symptoms.
C: Nijmegen breakage syndrome typically features microcephaly, growth retardation, and immunodeficiency, lacking the specific combination of eczema and thrombocytopenia evident in this case.
D: Omenn syndrome manifests with severe combined immunodeficiency and erythroderma, but does not align with the observed elevated IgE and IgA levels alongside thrombocytopenia seen in this child.
which of the following cells will be the last cell to perform its function in skin pathogen invasion
Rationale:
B: Naïve CD8 Lymphocytes will be the last cells to perform their function in skin pathogen invasion. These cells require activation and differentiation into effector cells, which takes additional time compared to others.
A: Natural killer cells respond rapidly to infected cells, acting as a first line of defense by recognizing and eliminating them quickly during pathogen invasion.
C: Intraepithelial Lymphocytes are already positioned within tissues and can quickly respond to pathogens, providing immediate defense before naïve cells are activated.
D: Macrophages are critical for phagocytosis and initiate an immune response promptly, thus performing their functions earlier in the invasion process than naïve CD8 Lymphocytes.
All of the following are actions of IL-1 EXCEPT
Rationale:
D: Decrease the permeability of the blood vessels. IL-1 primarily promotes inflammation and enhances vascular permeability, facilitating leukocyte migration and proliferation, making this option inconsistent with its known actions in immune responses.
A: Proliferation of WBCs stimulates the immune response, enhancing the body's ability to fight infections, which IL-1 directly influences by encouraging the growth of white blood cells.
B: Migration of WBCs to the site of inflammation is a key function of IL-1, as it signals immune cells to move toward areas requiring an immune response for healing.
C: Inflammatory response is a central function of IL-1, as it triggers and modulates various aspects of inflammation, promoting the body's defense mechanisms against pathogens and injury.
Which one of the following leukocytes is considered a 'granulocyte'?
Rationale:
B: Neutrophil. Neutrophils are classified as granulocytes due to their distinct granular cytoplasm containing enzymes that play a vital role in the immune response, particularly in fighting infections and inflammation.
A: Macrophage. Macrophages are large phagocytic cells that originate from monocytes and lack the granules that characterize granulocytes, thus placing them in a different leukocyte category.
C: Dendritic cell. Dendritic cells function primarily as antigen-presenting cells and do not contain granules, distinguishing them from granulocytes like neutrophils that possess specific granules for immune action.
D: Natural killer cell. Natural killer cells are lymphocytes involved in the innate immune response, targeting infected or cancerous cells, but they do not exhibit the granular structure typical of granulocytes.
The classical and alternative pathways meet at complement component:
Rationale:
C3. The classical and alternative complement pathways converge at complement component C3, which is pivotal for the opsonization, lysis of pathogens, and amplifying the complement response in immune defense mechanisms.
B: C4. While C4 is part of the classical pathway, it does not serve as the convergence point for both pathways, thus limiting its role in this context.
C: C4b. C4b is a fragment derived from C4 but does not represent the meeting point of the two pathways, lacking the broader functional implications of C3.
D: C5. C5 is involved later in the complement cascade and does not facilitate the initial convergence of classical and alternative pathways, making it an unsuitable choice.
A CD3pos cell that secretes perforin and granzyme is a:
Rationale:
Cytotoxic T cell.
Cytotoxic T cells, characterized by CD3 positivity, are essential for immune defense as they secrete perforin and granzyme, enabling them to induce apoptosis in infected or malignant cells effectively. This mechanism is crucial for controlling intracellular pathogens and tumor cells.
A: (γδ) T cell. These cells possess different surface markers and primarily respond to non-peptide antigens rather than secreting perforin and granzyme for direct cytotoxic activity.
B: Helper T cell. Although they express CD3 and assist in immune responses, helper T cells do not secrete perforin and granzyme; they primarily produce cytokines to activate other immune cells.
D: Regulatory T cell. These cells play a role in maintaining immune tolerance and preventing autoimmunity, but they do not secrete perforin and granzyme, as their function is to suppress immune responses.
A 4.5-year-old boy presented with history of recurrent attack of secretary otitis media and purulent nasal discharge, Haemophilus influenza revealed by culture of ear discharge, on physical examination there is no tonsillar tissue and no palpable lymph nodes. Of the following, the MOST appropriate test to confirm the diagnosis is
Rationale:
D: Antibodies to antigens of routine immunizations are vital for confirming the diagnosis of immunodeficiency. Given the boy's recurrent infections and absence of tonsillar tissue, evaluating his immune response is crucial.
A: Flow cytometry measures cell populations, not specific antibody levels. This method would not directly confirm the presence or absence of antibodies to routine immunization antigens.
B: IgA concentration focuses on a specific immunoglobulin class, which does not encompass the broader immune response needed to assess the effects of routine vaccinations.
C: Isohemagglutinins titer assesses blood group antibodies, not the immune response to vaccines. This test does not provide relevant information regarding the boy's susceptibility to recurrent infections.
A 15-year-old boy with rheumatoid arthritis, on quinine for 6 months, presented with fever, aphthous stomatitis, and fatigue for the last 5 days. His absolute neutrophil count (ANC) was 700/μL. The MOST next appropriate therapeutic measure to be done when quinine withdrawal fails to improve neutropenia is
Rationale:
Administration of recombinant human granulocyte colony-stimulating factor is the most appropriate next therapeutic measure. This treatment directly stimulates the bone marrow to increase neutrophil production, addressing the severe neutropenia effectively.
A: Administration of IVIG does not target the underlying issue of neutropenia and is generally used for immune modulation rather than directly stimulating neutrophil recovery in this scenario.
B: Aggressive use of antibiotics focuses on treating infections rather than resolving the neutropenia itself, which is the primary concern in this patient's clinical condition and requires specific intervention.
C: Transplantation of hematopoietic stem cells is a complex and invasive procedure reserved for severe cases, with significant risks and not suitable as a first-line response for drug-induced neutropenia.
Which of the following is a messenger that mediates the connection between the innate and adaptive immune systems?
Rationale:
Cytokines mediate the connection between the innate and adaptive immune systems by serving as signaling molecules that facilitate communication and coordination between various immune cells, enabling a robust immune response.
A: Complement components primarily function in the innate immune response, enhancing pathogen clearance through opsonization and lysis rather than mediating communication between immune system branches.
B: Vaccines stimulate the adaptive immune system by introducing antigens but do not serve as messengers that connect the innate and adaptive immune systems during immune responses.
C: T and B lymphocytes are integral components of the adaptive immune response, yet they do not act as mediators between the innate and adaptive systems, lacking a signaling role.
Macrophages
Rationale:
Macrophages perform phagocytosis and bacteriocidal mechanisms, as well as antigen presentation. This dual functionality allows them to effectively eliminate pathogens while also activating adaptive immunity by presenting antigens to T cells.
B: Lysis of some virally infected cells fails to encompass the broader roles of macrophages, which include phagocytosis and antigen presentation, essential for complete immune responses.
C: Killing parasites does not represent the primary functions of macrophages, which are more involved in phagocytosis and the presentation of antigens rather than targeting larger multicellular organisms.
D: Phagocytosis and bacteriocidal mechanisms alone overlook the critical role of antigen presentation, which is vital for initiating the adaptive immune response in conjunction with those processes.
A cluster of genes that encode proteins
Rationale:
A cluster of genes that encode proteins is the Major histocompatibility complex (MHC). The MHC is essential for immune response, as it encodes proteins that present antigens to T cells, facilitating recognition and activation during immune reactions, thus playing a crucial role in adaptive immunity and self/non-self discrimination.
A: B cell receptor (BCR) This option refers specifically to a membrane-bound immunoglobulin on B cells that recognizes antigens, rather than a gene cluster responsible for encoding proteins.
B: T cell receptor (TCR) This choice denotes a specific receptor on T cells that recognizes antigens presented by MHC, not a cluster of genes that encodes multiple proteins involved in immune response.
D: None of the above This option suggests that there are no relevant gene clusters, overlooking the fact that MHC is a well-defined cluster of genes integral to the immune system.
The aim of monoclonal antibody production is to produce cells that only secrete immunoglobulin directed against the antigen used in immunization. Which of the following hybridoma production steps is NOT correct?
Rationale:
Cells are cultured in a selective medium allowing fused and non-fused cells to survive. This step is not correct because only hybrid cells should survive, while non-fused cells must be eliminated to ensure purity.
A: Immunize a mouse with antigen of choice then remove the spleen when the mouse is making an antibody response. This step is essential for obtaining the necessary immune cells for fusion.
B: Fuse the immune spleen cells with a myeloma tumor cell. This action is crucial for creating hybridomas, which combine the desired antibody-producing cells with immortalized cells.
D: Cells are grown in individual culture plate wells, and culture supernatants from wells containing growing hybrid cells are screened for presence of desired antibody by an enzyme-linked immunosorbent assay (ELISA). Screening hybridomas for antibody production is a standard practice to identify successful fusions.
Penicillin can form a hapten-carrier conjugate with a self-protein that can then act as an immunogen and generate an immunoglobulin antibody, and can cross-react with a number of other antibiotics. This can complicate the treatment of bacterial infections in these patients because they are unable to take the antibiotics necessary to combat the infection.
Rationale:
Penicillin can induce the formation of IgE antibodies, which can lead to allergic reactions and complicate antibiotic treatment. This process involves the hapten-carrier conjugate interacting with self-proteins, leading to increased sensitivity.
A: IgA This antibody primarily plays a role in mucosal immunity and does not significantly contribute to the allergic response associated with penicillin.
B: IgD This immunoglobulin is primarily involved in the activation of B cells and does not play a significant role in drug allergies or cross-reactivity with antibiotics.
D: None of the above This option disregards the specific role of IgE in mediating allergic reactions related to penicillin, which is crucial in understanding the complications during treatment.
If alternative processing uses the second polyadenylation site, then what type of heavy chain mRNA is derived?
Rationale:
C: δ (delta)
Alternative processing at the second polyadenylation site results in the production of δ heavy chain mRNA. This process enables the generation of different immunoglobulin classes, specifically the delta chain variant.
A: α (alpha) The alpha heavy chain mRNA is derived from different polyadenylation processing, distinct from the second site utilized for the delta variant in alternative processing.
B: γ (gamma) The gamma heavy chain mRNA arises from first polyadenylation site selection, which is separate from the second polyadenylation site associated with delta mRNA production.
D: μ (mu) The mu heavy chain mRNA results from a unique polyadenylation process, not related to the alternative processing of the second polyadenylation site that produces delta heavy chain mRNA.
A TCR complex is comprised of the TCR, CD3 molecules, and which of the following CD3 chains?
Rationale:
A TCR complex is comprised of the TCR, CD3 molecules, and zeta (ζ) chains (two chains). The zeta chains are essential for transmitting signals upon TCR engagement, thus playing a vital role in T cell activation and function, enhancing the overall effectiveness of the immune response when the TCR recognizes an antigen.
A: Delta (δ) chain does not contribute to the TCR complex, which primarily consists of the TCR itself, CD3 molecules, and the zeta chains, making this option irrelevant.
B: Gamma (γ) chain is also not part of the TCR complex; the CD3 components specifically include epsilon and zeta chains, making this choice unaligned with the correct structure.
C: Epsilon (ε) chains (two chains) are part of the CD3 molecules but do not encompass the zeta chains, which are crucial for signal transduction within the TCR complex.
Evidence is accumulating showing that polymorphism in the MHC may be advantageous. Homozygosity at HLA class I has been shown to be a(n) with respect to HIV/AIDS. Similarly, there is evidence that homozygosity at HLA class II the risk of hepatitis B virus infection persisting.
Rationale:
Homozygosity at HLA class I has been shown to be a disadvantage with respect to HIV/AIDS. Evidence suggests that reduced genetic diversity in these alleles can impair immune response effectiveness, leading to higher susceptibility to infections.
A: Advantage; This option is misleading as it fails to recognize that enhanced genetic diversity typically provides better immune responses, thus supporting a disadvantageous view of homozygosity for HIV/AIDS.
B: Advantage; This choice inaccurately suggests that homozygosity increases protective effects, contradicting findings that link it to increased risks associated with HIV/AIDS and diminished immune response variability.
C: Disadvantage; While this option aligns with the idea of being detrimental, it incorrectly defines the relationship with hepatitis B virus infection, where homozygosity specifically increases persistent infection risks.
The transporter associated with antigen presentation (TAP) the peptides to traverse the membrane bilayer of the endoplasmic reticulum and bind in the empty peptide-binding groove of nascent MHC molecules being synthesized in the endoplasmic reticulum.
Rationale:
TAP permits Class I peptides to traverse the membrane bilayer of the endoplasmic reticulum, facilitating their binding in the peptide-binding groove of nascent MHC Class I molecules.
B: Permits; Class II. TAP primarily interacts with Class I molecules, not Class II, which processes exogenous antigens differently and does not rely on TAP for peptide transport.
C: Does not allow; Class I. TAP actively facilitates the transport of peptides for Class I molecules, contradicting the assertion that it does not allow this process.
D: Does not allow; Class II. Class II molecules are not involved in TAP’s function, as they primarily present extracellular antigens and utilize a different pathway for peptide acquisition.
Phagocytose, bacteriocidal activity, ADCC
Rationale:
Neutrophils exhibit phagocytosis, bacteriocidal activity, and antibody-dependent cellular cytotoxicity (ADCC).
Neutrophils are the primary immune cells responsible for engulfing pathogens through phagocytosis, releasing enzymes for bactericidal action, and mediating ADCC to eliminate infected cells, showcasing their vital role in the innate immune response.
A: Natural Killer (NK) cells primarily target virus-infected and tumor cells, relying on cytotoxic mechanisms rather than phagocytosis, making them less involved in direct bactericidal activity.
C: Basophils play a role in allergic responses and release histamine, but they do not engage in phagocytosis or bacteriocidal functions, limiting their effectiveness against pathogens.
D: T-cytotoxic cells specialize in recognizing and destroying virus-infected or cancerous cells, focusing on adaptive immunity rather than the innate immune functions of phagocytosis or direct bactericidal activity.
Which of the following locations has cell that transport the antigens by transcytosis into sub-epithelial tissues (e.g. lamina propria) where they encounter lymphocytes?
Rationale:
C: Peyer's patches (gut-associated lymphoid tissue, GALT) are specialized structures that facilitate the transport of antigens via transcytosis into sub-epithelial tissues, allowing for effective interaction with lymphocytes in the lamina propria.
A: Tonsils (nasopharyngeal-associated lymphoid tissue, NALT) primarily function to trap pathogens but do not have the specific transcytosis mechanism to transport antigens into sub-epithelial tissues effectively.
B: Adenoids (nasopharyngeal-associated lymphoid tissue, NALT) serve similar roles as tonsils in immune defense but lack the specific structures required for transcytosis of antigens into the lamina propria.
D: Axilla (lymph node center) pertains to general immune cell activity but does not specifically involve the transcytosis of antigens into sub-epithelial tissues for lymphocyte encounters.
Tolerance refers to the ability of B cells to:
Rationale:
B cells demonstrate tolerance primarily by recognizing and not responding to self antigens. This ability is crucial to prevent autoimmune reactions and maintain the body’s immune balance, ensuring self-tolerance.
A: Tolerate T cells. B cells do not primarily engage in tolerating T cells; their main function involves managing self antigens to avoid inappropriate immune responses.
B: Tolerate other B cells. Tolerance among B cells is not their main function; rather, their role centers on distinguishing between self and non-self antigens for immune regulation.
D: Tolerate foreign antigens. While B cells can recognize foreign antigens, tolerance specifically refers to their ability to ignore self antigens, preventing harmful immune reactions against the body’s own tissues.
The γδ T cell acts as a part of the first line of defense, recognizing microbial invaders. They appear to recognize commonly occurring microbial pathogens. Where can γδ T cells be found?
Rationale:
γδ T cells can be found in the skin and gut mucosa. These locations are critical as they serve as primary entry points for microbial pathogens, allowing γδ T cells to respond swiftly to infections.
A: Liver and kidney These organs are primarily involved in filtering blood and metabolic regulation, not in direct immune surveillance against microbial pathogens as seen in the skin and gut.
B: Bone marrow and spleen While essential for immune cell development and maturation, these sites do not have the same immediate exposure to microbial invaders as the skin and gut mucosa do.
D: Respiratory tract and bone marrow Although the respiratory tract is important for defense, the bone marrow lacks direct contact with external pathogens, unlike the skin and gut mucosa.
Antiapoptotic molecules are encoded by the death-inhibiting family of bcl genes.
Rationale:
Antiapoptotic molecules are encoded by the death-inhibiting family of bcl genes. This statement is accurate as bcl genes play a critical role in preventing apoptosis, thus promoting cell survival and contributing to various cellular processes.
B: FALSE This choice suggests that the statement about bcl genes is inaccurate, disregarding their established function in apoptosis regulation and the essential role they play in maintaining cellular homeostasis.
To prevent inadvertent complement activation, eight inhibitors exist. Which of the following is an inhibitor preventing activation of C2 and C4, and prevents C3 activation by the alternative pathway?
Rationale:
To prevent inadvertent complement activation, the C1 inhibitor functions effectively. This inhibitor specifically targets the activation of C2 and C4, while also preventing C3 activation through the alternative pathway, thereby maintaining complement balance.
B: C2 inhibitor This option implies a targeted inhibition of C2, which does not encompass the broader role of preventing C3 activation through alternative pathways.
C: C3 inhibitor This choice focuses solely on inhibiting C3, neglecting the critical prevention of C2 and C4 activation necessary for comprehensive complement regulation.
D: C4 inhibitor This selection suggests inhibition of C4 exclusively, overlooking the importance of C1 in preventing both C2 activation and C3 activation through alternative pathways.
Enhance diapedesis and stimulate TH2 responses
Rationale:
Cytokines/IL-4 enhance diapedesis and stimulate TH2 responses. IL-4 specifically promotes the differentiation of naive T cells into TH2 cells and increases the expression of adhesion molecules, facilitating diapedesis in the immune response.
A: Trypase & Chemotrypsin These proteases primarily function in digestion and do not play a direct role in enhancing diapedesis or stimulating TH2 cell responses in the immune context.
B: Histamine While histamine is involved in inflammatory responses, it primarily mediates vasodilation and increased vascular permeability rather than directly enhancing diapedesis or specifically promoting TH2 responses.
D: Cytokines/TNF TNF is predominantly associated with promoting inflammatory responses and activating macrophages, rather than specifically enhancing diapedesis or stimulating the differentiation of TH2 cells in the immune system.
Immunostimulatory complexes (ISCOMS) can be used for mucosal vaccines and induce widespread mucosal immunity in the gut and respiratory tract. They are the one way that response can be promoted.
Rationale:
Cytotoxic T cell. Cytotoxic T cells play a crucial role in mucosal vaccines by directly targeting and eliminating infected cells, thus promoting a robust immune response in both the gut and respiratory tract.
A: B cell. B cells primarily produce antibodies and are essential for humoral immunity, but they do not directly induce cell-mediated immunity like cytotoxic T cells do.
B: Helper T cell. Helper T cells assist in activating other immune cells but do not directly kill infected cells or induce widespread mucosal immunity as cytotoxic T cells do.
D: Macrophage. Macrophages are important for phagocytosis and antigen presentation, yet they do not directly mediate the specific immune responses associated with cytotoxic T cells in mucosal contexts.
A patient is being seen for recurrent infections. However, the patient does not seem to think anything special of these infections and there has been no previous diagnosis other than the infections. Lab work reveals abnormalities with hypochlorous acid and H2O2 conversion. Which of the following is the most likely?
Rationale:
Myeloperoxidase deficiency. This condition leads to impaired conversion of hypochlorous acid and H2O2, resulting in recurrent infections, as the body struggles to effectively combat pathogens, despite the patient’s indifference to these infections.
A: Ataxia telangiectasia. This disorder involves immunodeficiency along with neurological problems, which is not indicated here, making it less likely given the focus on recurrent infections without neurological symptoms.
B: Wiskott-Aldrich syndrome (WAS). This syndrome presents with eczema, thrombocytopenia, and recurrent infections, but the specific lab abnormalities related to hypochlorous acid and H2O2 conversion do not align with WAS.
C: Hereditary angioedema. Characterized by recurrent swelling episodes, this condition does not involve recurrent infections or the specific enzymatic deficiencies indicated in the lab work presented for this patient.