A patient encounters the helminth Onchcerca volvulus after swimming in a parasite-infested river in West Africa. Following interaction with the patient's innate immune system, one would expect and hope for the development of which subtype of T cells in response to the organism?
Rationale:
C: Th2 cells play a crucial role in the immune response to helminth infections like Onchocerca volvulus. They promote antibody production and orchestrate a response that effectively combats parasitic invasions, especially in allergic and anti-parasitic contexts.
A: Tho cells are a less defined subset and do not specifically target helminths, making them unsuitable for addressing the unique challenges posed by parasitic infections such as those caused by Onchocerca volvulus.
B: Thr cells are primarily involved in regulating immune responses to pathogens and do not specialize in combating helminth infections, which require a robust immune activation typically associated with Th2 cells.
D: Treg cells are essential for maintaining immune tolerance and preventing excessive inflammation, but they do not actively promote the immune response necessary to effectively eliminate helminth infections like Onchocerca volvulus.
The normal immunological control of tumors is referred to as?
Rationale:
Immune surveillance. This concept describes the process where the immune system actively monitors and detects tumor cells, identifying and eliminating them before they can grow and spread.
A: Immunological tolerance. This refers to the immune system's ability to avoid attacking the body’s own tissues, which is distinct from actively targeting tumor cells.
C: Type III hypersensitivity. This involves immune complex-mediated reactions that cause tissue damage, not the proactive identification and destruction of cancer cells seen in immune surveillance.
D: Immunological silence. This term indicates a state where the immune response is minimal or absent, contrasting with the dynamic activity of immune surveillance against tumors.
Which one of the following sets of cells can present antigen to helper T cells?
Rationale:
Helper T cells require antigen-presenting cells to activate their immune response, and B cells along with dendritic cells are known for their ability to efficiently present antigens to these T cells.
A: B cells and dendritic cells This option is accurate as both cell types express major histocompatibility complex (MHC) molecules, crucial for presenting processed antigens to helper T cells, thereby facilitating adaptive immunity.
B: B cells and cytotoxic T cells Cytotoxic T cells primarily kill infected cells rather than present antigens. This combination lacks the necessary antigen-presenting capabilities needed for helper T cell activation.
C: Macrophages and eosinophils While macrophages can present antigens, eosinophils are primarily involved in combating parasitic infections and do not function as antigen-presenting cells for helper T cell activation.
D: Neutrophils and cytotoxic T cells Neutrophils mainly engage in phagocytosis and do not present antigens. Cytotoxic T cells specialize in targeting infected cells rather than presenting antigens to helper T cells.
Matching: Immunodeficiency - Lymphopenia plus severe neutropenia
Rationale:
Lymphopenia plus severe neutropenia characterizes reticular dysgenesis, which results in a profound deficiency of all immune cell lineages, leading to an extreme vulnerability to infections.
A: Severe combined immunodeficiency (SCID) primarily features both T-cell and B-cell deficiencies, without the distinctive severe neutropenia that characterizes reticular dysgenesis, thus presenting a different clinical picture.
B: Omenn syndrome is characterized by T-cell deficiency with eosinophilia and skin rashes, differing fundamentally from reticular dysgenesis, which shows profound impairment across multiple immune cell types.
D: Adenosine deaminase (ADA) deficiency causes immune dysfunction mainly through T-cell impairment, but it does not present with the severe neutropenia that defines reticular dysgenesis, leading to different symptoms.
A 6-month-old presents with recurrent cellulitis and bacteremias due to Staphylococcus aureus. The white blood cell count is 2500 with 5% neutrophils, 10% eosinophils, 35% monocytes, and 50% lymphocytes. The platelet count is 650,000. A brother and a female cousin died at the age of 18 months and 2 years, respectively. The most likely diagnosis is
Rationale:
Kostmann disease. This condition, characterized by severe congenital neutropenia, leads to recurrent infections from pathogens like Staphylococcus aureus, aligning with the patient's symptoms and family history of early mortality.
A: AIDS. The white blood cell count and lymphocyte percentage do not suggest an immunodeficiency consistent with AIDS. This condition typically presents with low CD4 counts and opportunistic infections.
B: severe combined immunodeficiency. The elevated lymphocyte level and specific infection pattern do not match the classic presentation of SCID, which usually involves profound lymphopenia and susceptibility to a broader range of infections.
D: cyclic neutropenia. This disorder causes periodic drops in neutrophil counts, but the patient’s consistent low neutrophil percentage and recurrent infections indicate a more permanent deficiency rather than cyclical fluctuations.
Light microscopy of neutrophils for the presence of giant granules can help to diagnose
Rationale:
Giant granules in neutrophils are indicative of Chédiak-Higashi syndrome, a genetic disorder characterized by immunodeficiency and partial oculocutaneous albinism. Light microscopy effectively reveals these granules, aiding in diagnosis.
A: chronic granulomatous disease This condition primarily affects the ability of neutrophils to produce reactive oxygen species, leading to increased susceptibility to infections, not the presence of giant granules.
C: hyperimmunoglobulin E (Job syndrome) This syndrome involves elevated IgE levels and recurrent infections but does not feature the distinct giant granules found in Chédiak-Higashi syndrome.
D: glucose-6-phosphate dehydrogenase deficiency This metabolic disorder affects red blood cells, leading to hemolytic anemia rather than impacting neutrophil granule morphology or presence of giant granules.
which of the following is a Pathogen associated molecular pattern
Rationale:
Double stranded Viral RNA. This molecule is recognized by the immune system as a characteristic of viral infections, triggering an immune response as a Pathogen Associated Molecular Pattern (PAMP) that indicates the presence of pathogens.
B: LPS. While LPS is a PAMP found in bacterial cell walls, it specifically pertains to gram-negative bacteria, not viruses like double-stranded RNA does.
C: HMGb1 (High mobility group box 1). HMGb1 is a nuclear protein that can act as a damage-associated molecular pattern (DAMP) rather than a PAMP, distinguishing it from pathogen-specific molecules.
D: Peptidoglycan. This structure is a component of bacterial cell walls and serves as a PAMP, but it is not associated with viral pathogens, unlike double-stranded RNA.
Which of the following best describes complementary system
Rationale:
A: A group of carbohydrates and lipids that circulate in the blood and a part of immune system. This description inaccurately focuses on carbohydrates and lipids, which do not define the complementary system's primary function or components.
C: Always activated proteins circulate in blood. Complement proteins are not always activated; they require specific triggers for activation, distinguishing them from this description of constant circulation.
D: None of the above. This option fails to acknowledge that the complementary system is indeed characterized by a group of proteins involved in opsonization and inflammatory responses, making it invalid.
Macrophages recognize microorganisms through the Interaction of their substances with what receptor?
Rationale:
Macrophages recognize microorganisms through the interaction of their substances with PRR. Pattern Recognition Receptors (PRRs) enable macrophages to detect pathogen-associated molecular patterns, triggering immune responses essential for combating infections effectively.
A: antigen receptor Recognizing specific antigens is a function of B and T cells, not macrophages, which primarily utilize PRRs for broader pathogen detection.
B: complement receptor While complement receptors assist in opsonization, they do not directly mediate the recognition of microorganisms, which is primarily the role of PRRs.
C: membrane IG Membrane immunoglobulin pertains to B cells and their antigen recognition, unlike macrophages, which rely on PRRs for identifying various pathogens in the immune response.
A 66-year-old man with advanced pancreatic cancer develops cachexia (loss of mass) Which cytokine is primarily responsible for the cachexia seen in certain patients with cancer or debilitating infections?
Rationale:
Tumor necrosis factor is primarily responsible for the cachexia observed in patients with advanced cancer. This cytokine promotes inflammation and metabolism alterations, leading to muscle and fat tissue breakdown, characteristic of cancer cachexia.
A: Interferon-α This cytokine plays a role in immune response but does not directly induce the metabolic changes associated with cachexia in cancer patients.
B: Interleukin-7 This cytokine is involved in lymphocyte development and immune function, lacking the specific impact on weight loss and muscle wasting seen in cachexia.
C: Interleukin-17 While it contributes to inflammatory responses, it does not specifically mediate the cachectic process associated with cancer or debilitating infections leading to significant weight loss.
Which of the following peripheral immune tissues is likely to be different from teen through life to old age?
Rationale:
C: thymus. The thymus is critical for T-cell development and undergoes significant involution with age, leading to a decrease in its size and function, which markedly differs from other immune tissues throughout life.
A: spleen. The spleen maintains its structural and functional roles throughout life, continuously filtering blood and responding to pathogens without significant age-related changes in its primary functions.
B: MALTs. Mucosa-associated lymphoid tissues remain relatively stable across the lifespan, providing localized immune responses that adapt but do not drastically change with aging compared to the thymus.
D: lymph nodes. Lymph nodes retain their essential roles in immune surveillance and response throughout life, demonstrating continuity in structure and function without the pronounced age-related decline seen in the thymus.
Which of the following statements is TRUE regarding diurnal variation of the absolute eosinophil count (AEC)?
Rationale:
Diurnal variation of the absolute eosinophil count (AEC) is lower in the early morning.
This statement is accurate as research indicates that eosinophil levels tend to be at their lowest during the early morning hours, likely linked to hormonal fluctuations and circadian rhythms affecting immune responses and cell distribution throughout the day.
A: higher in the evening Eosinophil levels typically increase as the day progresses, peaking in the late evening, making this statement inconsistent with established diurnal patterns.
B: lower in the afternoon Afternoon levels of eosinophils generally rise compared to the early morning, contradicting this option's assertion about reduced counts during that time.
C: higher in the afternoon While eosinophil counts do increase in the afternoon, they do not reach the peak levels seen in the evening, thus making this statement misleading.
The diagnosis of chronic granulomatous disease CGD is MOST often made by
Rationale:
The diagnosis of chronic granulomatous disease (CGD) is most often made by the nitroblue tetrazolium dye test. This test effectively identifies the inability of neutrophils to produce reactive oxygen species, which is a hallmark of CGD, confirming the diagnosis through observable cellular dysfunction.
A: DNA analysis This method can identify genetic mutations associated with CGD, but it is not the primary diagnostic tool typically employed in clinical practice for initial diagnosis.
B: flow cytometry This technique can assess cell populations and functions but does not directly evaluate the oxidative burst capacity of neutrophils, which is crucial for diagnosing CGD.
C: neutrophil G6PD assay Although this test assesses enzyme activity, it does not specifically indicate the oxidative capacity of neutrophils, which is essential in diagnosing chronic granulomatous disease.
Which of the following components of the innate immune system involves recognition molecules such as mannan-binding lectin (MBL) for bacteria with mannose on the surface?
Rationale:
B: The complement system involves recognition molecules like mannan-binding lectin (MBL) that identify bacteria with mannose on their surfaces, facilitating opsonization and promoting an effective innate immune response.
A: Natural killer (NK) cells primarily target virus-infected and tumor cells, lacking the specific recognition function for bacterial surface structures like mannose, thus not engaging in this process.
C: Oxygen dependent and independent killing refers to mechanisms used by phagocytes to destroy pathogens, but doesn’t involve recognition molecules like MBL, which are essential for targeting specific bacteria.
D: Interferons are signaling proteins that play a role in antiviral defense and immune regulation, but they do not directly recognize or bind to bacterial surface structures such as mannose.
Eventual elimination of antigen
Rationale:
The eventual elimination of antigen occurs during the effector phase. This phase is characterized by the full activation of immune cells that directly target and destroy antigens, ensuring their removal from the body.
A: Cognitive phase This phase involves the recognition and processing of antigens, but it does not directly lead to their elimination from the body.
B: Activation phase This phase focuses on the stimulation and proliferation of immune cells, preparing them for action but not executing the elimination of antigens.
D: None of the above This option suggests that no phase accounts for antigen elimination, which contradicts the established roles of the effector phase in the immune response.
Given that an individual's parents have completely different HLA genes, that individual will have about different class I and II MHC molecules on the surface of certain of their lymphoid cells.
Rationale:
D: An individual with completely different HLA genes from their parents can express a diverse set of class I and II MHC molecules, totaling 12 distinct variations on lymphoid cell surfaces.
A: 3 Only a minimal number of variations would result from two different parental HLA genes, which does not account for the full diversity present in MHC molecules.
B: 6 This option represents a limited combination of MHC molecules, failing to encompass the extensive genetic diversity provided by both parents' distinct HLA genes.
C: 9 While this number suggests some variation, it underestimates the potential combinations available from the unique contributions of both parents' HLA genes.
Has different subtypes
Rationale:
IgG has different subtypes. IgG is the most abundant antibody in the bloodstream and is classified into four distinct subtypes (IgG1, IgG2, IgG3, and IgG4), each with unique functions and properties, tailoring the immune response to various pathogens.
B: IgE primarily mediates allergic reactions and defense against parasitic infections, lacking distinct subtypes, making it less versatile compared to IgG.
C: IgM is the first antibody produced in response to an infection, but it does not have subtypes. Its primary role is in initial immune response.
D: IgG & IgM includes IgG, which has subtypes, but IgM does not, making this combination misleading regarding the presence of different subtypes in both antibodies.
Each polypeptide chain (heavy and light) on immunoglobulin has a variable (V) and constant (C) region. Immunoglobulin chains are encoded by that is/are rearranged during development to assemble a functional gene encoding either a heavy or a light chain.
Rationale:
Sets of gene segments; B cell. The immunoglobulin chains are formed through the rearrangement of various gene segments during B cell development, creating diverse heavy and light chains essential for effective immune responses.
A: A single continuous DNA sequence; B cell. Immunoglobulin chains cannot be encoded by a single DNA sequence; they require the rearrangement of multiple gene segments for proper functionality.
B: A single continuous DNA sequence; T cell. T cells do not utilize a continuous DNA sequence for their receptor formation; they also depend on rearranged gene segments for functionality.
D: Sets of gene segments; T cell. T cells have their own unique gene rearrangement processes, but they are specifically for T cell receptors, not immunoglobulin chains.
Which of the following TCR genetic chains contain D-segments, similar to immunoglobulin heavy chains?
Rationale:
C: Beta (β); Delta (δ) TCR chains contain D-segments, paralleling the structure of immunoglobulin heavy chains. This similarity is crucial for the diversity and functionality of T-cell receptors in adaptive immunity.
A: Alpha (α); Beta (β) The alpha chain lacks D-segments, which distinguishes it from immunoglobulin heavy chains. Only the beta chain possesses D-segments, making this option incomplete.
B: Delta (δ); Gamma (γ) The gamma chain does not include D-segments, setting it apart from immunoglobulin heavy chains. Therefore, this pairing does not align with the specified structural characteristics.
D: Gamma (γ); Alpha (α) Both chains in this option lack D-segments, failing to match the immunoglobulin heavy chain structure. This absence renders the option invalid in the context of the question.
Class III MHC genes encode for which of the following?
Rationale:
Class III MHC genes encode complement molecules. These genes play a vital role in the immune response by producing proteins involved in the complement system, which enhances the ability to clear pathogens.
A: CD4+ T cells These cells are primarily associated with Class II MHC molecules, which present antigens to helper T cells, rather than being encoded by Class III MHC genes.
B: CD8+ T cells CD8+ T cells interact with Class I MHC molecules, focusing on cytotoxic responses against infected cells, making them unrelated to Class III MHC gene functions.
D: Cytokine molecules While cytokines are crucial for immune signaling, they are not directly encoded by Class III MHC genes, which are specific to complement proteins instead.
Directly: some recognize nonpeptide phosphorylated lipids and carbohydrates; other recognize antigen that have not been processed
Rationale:
Some recognize nonpeptide phosphorylated lipids and carbohydrates; other recognize antigen that have not been processed.
C: TCR γδ specifically recognizes non-peptide antigens, including phosphorylated lipids and carbohydrates, allowing T cells to respond to a broader range of antigens that are not traditionally processed.
A: Immunoglobulin primarily binds to processed peptide antigens presented by major histocompatibility complex (MHC) molecules, thus not recognizing unprocessed antigens or nonpeptide structures effectively.
B: TCRαβ mainly recognizes peptide antigens presented by MHC, failing to interact with nonpeptide phosphorylated lipids and carbohydrates or unprocessed antigens, limiting its recognition scope.
D: None of the above suggests that no option is valid; however, TCR γδ indeed recognizes nonpeptide antigens, making this option inaccurate in the context provided.
Protein antigens bound to complement component C3d can bind simultaneously to both and the BCR. This enables the co-receptor complex to cluster and crosslink with the BCR, inducing phosphorylation.
Rationale:
Protein antigens bound to complement component C3d can bind simultaneously to both CD21 and the BCR. This interaction facilitates the clustering and crosslinking of the co-receptor complex with the BCR, leading to phosphorylation.
A: CD19 Antigens do not directly bind to CD19 in the same manner, which limits its role in the co-receptor complex's interaction with the BCR and phosphorylation.
B: CD20 Lacks the ability to bind complement components like C3d, therefore, it does not participate in the clustering and crosslinking necessary for the phosphorylation event described.
D: CD81 This molecule does not interact directly with complement components, thus failing to facilitate the simultaneous binding required for effective co-receptor complex formation and subsequent signaling.
In the embryonic human, the primary lymphoid organs are initially in the yolk sac, then in the fetal , and finally in the
Rationale:
The primary lymphoid organs in the embryonic human are initially in the yolk sac, then in the fetal liver, and finally in the bone marrow and thymus.
The fetal liver serves as a key site for hematopoiesis and immune cell development before the bone marrow takes over this function, with the thymus playing a critical role in T-cell maturation.
A: Spleen and kidneys; The kidneys do not serve as primary lymphoid organs during development, and the spleen primarily functions in later immune responses rather than early lymphocyte production.
B: Spleen and thymus; While the thymus is involved in T-cell maturation, the spleen does not act as a primary lymphoid organ during the early stages of embryonic development.
C: Kidneys and thymus; The kidneys are not primary lymphoid organs during embryonic development, and while the thymus is important, it cannot be paired with the kidneys for this context.
Which of the following has the surface marker CD34 instead of the surface marker CD19, during B cell development?
Rationale:
Stem cell
During B cell development, stem cells express CD34 as a surface marker, indicating their undifferentiated state. This marker is essential for identifying hematopoietic stem cells before they progress to more specialized B cell stages.
B: Pro-B cell
Pro-B cells begin expressing CD19 as they start to differentiate, marking a transition away from the stem cell stage and indicating their commitment to B cell lineage.
C: Early pre-B cell
Early pre-B cells have already transitioned from expressing CD34 to CD19, reflecting their further maturation and development within the B cell pathway.
D: Late pre-B cell
Late pre-B cells predominantly express CD19, signifying advanced differentiation and preparation for antigen receptor expression, moving away from the earlier stem cell characteristics.
Where are double-positive (DP) cells found?
Rationale:
Double-positive (DP) cells are found in the thymus cortex.
This region is where T-cells undergo maturation and selection, specifically expressing both CD4 and CD8 co-receptors, allowing them to develop further into functional T-cells essential for immune responses.
A: Bone marrow Double-positive cells are not located in the bone marrow, as this site primarily serves as the origin for hematopoietic stem cells and early immune cell development.
B: Thymus subcapsular zone The subcapsular zone is responsible for the initial stages of thymocyte development, where cells are predominantly single-positive, lacking the double-positive characteristic found in the cortex.
D: Thymus medulla The medulla primarily contains mature T-cells, where negative selection occurs, but it does not house the double-positive cells essential for the maturation process that occurs in the cortex.
T cell activation of TH1 leads to ___ antibody production and opsonization (or macrophage activation). Activation of TH2 leads to ___ antibody production and activation of mast cells and eosinophils.
Rationale:
TH1 activation leads to IgG antibody production and opsonization, while TH2 activation results in IgE antibody production and the activation of mast cells and eosinophils.
TH1 cells primarily stimulate IgG, enhancing opsonization for macrophages. TH2 cells focus on IgE production, crucial for responses against parasites and allergens, distinguishing their roles in immune responses.
A: CD4+; IgE; IgG. This option misplaces the antibody types associated with each T cell subset, attributing IgE production to TH1 instead of TH2.
C: CD8+; IgE; IgG. CD8+ T cells are cytotoxic and do not primarily trigger IgE or IgG production, which is specific to CD4+ T cells.
D: CD8+; IgG; IgE. Similar to C, CD8+ T cells do not mediate the antibody responses described, which are characteristic of CD4+ T cell subsets.
Which of the following is NOT true regarding interferon?
Rationale:
Interferon inactivates antigen-presenting cells. This statement is false, as interferon actually enhances the function of these cells, promoting immune responses rather than inhibiting their activity in the context of viral infections.
A: Interferon prevents infection spreading from cell to cell. This is true since interferon induces an antiviral state in neighboring cells, limiting viral replication and spread.
B: NK cells are activated by interferon and lyse infected cells. This holds true, as interferon stimulates natural killer cells, enhancing their ability to identify and destroy infected cells.
D: Interferon is viral specific, attacking viral proteins. This statement is misleading, as interferon broadly influences the immune response rather than targeting specific viral proteins, acting against a range of viruses.
What is the primary response seen in acute-phase responses to infection?
Rationale:
Increased body temperature.
During acute-phase responses to infection, the body elevates its temperature as a defense mechanism, enhancing immune function and inhibiting pathogen replication. This physiological response helps the body combat infections more effectively, showcasing its importance in the healing process.
A: Decreased blood pH. Lowering blood pH does not typically occur during acute-phase responses; instead, the body seeks to maintain homeostasis while fighting off infections.
B: Decreased metabolic pH. Metabolic pH generally remains stable during infections, as the body prioritizes defense mechanisms over alterations in metabolic processes, which could hinder recovery.
D: Increased heart rate. While heart rate may rise in response to infection, it is not the primary response seen; the increase in body temperature plays a more crucial role in combating pathogens.
Degrade host cell proteins, activate caspase enzyme system
Rationale:
Degrade host cell proteins, activate caspase enzyme system.
Granzyme is a serine protease that enters target cells and cleaves specific substrates, leading to the degradation of host cell proteins and the activation of the caspase enzyme cascade, ultimately resulting in apoptosis.
A: Perforin facilitates the entry of granzymes into cells but does not directly degrade proteins or activate caspases on its own.
C: Fas ligand engages with the Fas receptor to induce apoptosis but does not degrade proteins or directly activate caspases like granzyme does.
D: None of the above does not apply, as granzyme specifically performs the functions described in the question, making this option irrelevant.
A patient presents in the winter months with swollen lips. The patient says they forgot their lip balm. Uncontrolled activation of the classical complement pathway is responsible for the swelling. Records show the patient has a C1 inh deficiency. Which of the following does this patient have?
Rationale:
Hereditary angioedema. The patient's symptoms of swollen lips, combined with a deficiency in C1 inhibitor and uncontrolled complement activation, are characteristic of hereditary angioedema, leading to recurrent episodes of swelling.
A: C5-C9 deficiency. This condition primarily results in increased susceptibility to certain infections, particularly Neisseria species, rather than localized swelling of tissues like the lips observed in this patient.
B: Glucose-6-phosphate dehydrogenase deficiency. This enzymatic deficiency leads to hemolytic anemia and does not cause localized swelling or relate to complement system deficiencies as seen in hereditary angioedema.
D: Severe combined immunodeficiency disease (SCID). SCID involves profound immune deficiency, primarily affecting T and B cells, which does not align with the swelling symptoms caused by complement pathway dysregulation.
A patient encounters the helminth Onchcerca volvulus after swimming in a parasite-infested river in West Africa. Following interaction with the patient's innate immune system, one would expect and hope for the development of which subtype of T cells in response to the organism?
Rationale:
The development of Th2 cells is expected in response to Onchocerca volvulus. Th2 cells play a pivotal role in orchestrating the immune response against helminth infections by promoting IgE production, eosinophil activation, and mast cell degranulation, which are crucial for combating parasitic worms.
A: Tho This subtype is associated with inflammatory responses, particularly in combating intracellular pathogens, rather than the specific immune mechanisms required for helminth defense.
B: Thr This T cell subtype is linked to regulatory functions and does not primarily engage in the immune response against parasitic infections like those caused by helminths.
D: Treg Regulatory T cells primarily function to maintain immune tolerance and prevent excessive inflammation, which is counterproductive in the context of fighting a helminth infection.
The normal immunological control of tumors is referred to as?
Rationale:
Immune surveillance. This term describes the body's ongoing monitoring for abnormal cells, enabling the immune system to detect and eliminate potential tumors before they can develop further, thereby maintaining cellular integrity.
A: Immunological tolerance. This concept refers to the immune system's inability to respond to specific antigens, often leading to a lack of defense against tumors rather than proactive surveillance.
C: Type III hypersensitivity. This type of hypersensitivity involves immune complex-mediated reactions, which are unrelated to the protective mechanisms against tumor formation and do not reflect normal immunological tumor control.
D: Immunological silence. This term indicates a state where the immune system is inactive or unresponsive, failing to act against tumors, which contradicts the necessary active monitoring of immune surveillance.
Which one of the following sets of cells can present antigen to helper T cells?
Rationale:
B cells and dendritic cells can present antigen to helper T cells.
B cells and dendritic cells are specialized antigen-presenting cells equipped to process and present antigens via Major Histocompatibility Complex (MHC) class II molecules, crucial for activating helper T cells and initiating adaptive immune responses. Their unique abilities enable them to interact effectively with T cell receptors, ensuring a robust immune system activation.
B: B cells and cytotoxic T cells. Cytotoxic T cells primarily recognize and kill infected cells rather than presenting antigens, thereby lacking the necessary function to activate helper T cells.
C: Macrophages and eosinophils. While macrophages can present antigens, eosinophils primarily target parasitic infections and lack the primary role in antigen presentation to helper T cells.
D: Neutrophils and cytotoxic T cells. Neutrophils are primarily effector cells that respond to infections and do not present antigens, while cytotoxic T cells perform killing, not antigen presentation.
Matching: Immunodeficiency - Lymphopenia plus severe neutropenia
Rationale:
Lymphopenia plus severe neutropenia is characteristic of reticular dysgenesis. This condition involves a profound deficiency in both T cells and myeloid cells, leading to severe immune dysfunction.
A: Severe combined immunodeficiency (SCID) typically presents with lymphopenia but not always with significant neutropenia, thus not fitting the specified combination of symptoms.
B: Omenn syndrome features lymphadenopathy and eczema alongside immunodeficiency, deviating from the specific lymphopenia plus severe neutropenia profile stated in the question.
D: Adenosine deaminase (ADA) deficiency leads to a specific type of lymphopenia, primarily affecting T cells, without the pronounced neutropenia seen in reticular dysgenesis.
A 6-month-old presents with recurrent cellulitis and bacteremias due to Staphylococcus aureus. The white blood cell count is 2500 with 5% neutrophils, 10% eosinophils, 35% monocytes, and 50% lymphocytes. The platelet count is 650,000. A brother and a female cousin died at the age of 18 months and 2 years, respectively. The most likely diagnosis is
Rationale:
Kostmann disease is the most likely diagnosis. This condition is characterized by severe neutropenia leading to recurrent infections, as evidenced by the low neutrophil count and familial history of early deaths due to similar infections.
A: AIDS presents with immunosuppression but doesn't typically show such a specific neutrophil deficiency and family history of early mortality in this manner.
B: Severe combined immunodeficiency involves both T and B cell deficiencies, which is not indicated by the lymphocyte profile here.
D: Cyclic neutropenia is characterized by periodic neutrophil fluctuations, rather than the consistently low neutrophil level observed in this patient.
Light microscopy of neutrophils for the presence of giant granules can help to diagnose
Rationale:
Giant granules in neutrophils indicate Chédiak-Higashi syndrome. This condition is characterized by immunological defects and abnormal granule formation, making light microscopy a valuable diagnostic tool for identifying the disease.
A: chronic granulomatous disease Neutrophils in this condition show normal granule morphology, while the defect lies in the ability to respond to pathogens, not in granule size or presence.
C: hyperimmunoglobulin E (Job syndrome) This syndrome involves elevated immunoglobulin levels and recurrent infections but does not present with giant granules in neutrophils, distinguishing it from Chédiak-Higashi syndrome.
D: glucose-6-phosphate dehydrogenase deficiency This metabolic disorder primarily affects red blood cells and does not influence neutrophil granule morphology, making it unrelated to the diagnosis of giant granules.
which of the following is a Pathogen associated molecular pattern
Rationale:
Double stranded Viral RNA. This molecule is recognized by the immune system as a pathogen-associated molecular pattern (PAMP), triggering a response to viral infections and enhancing host defense mechanisms against pathogens.
B: LPS LPS (lipopolysaccharide) is a PAMP found in bacterial cell walls, but it specifically pertains to Gram-negative bacteria, making it contextually distinct from viral components like RNA.
C: HMGb1 (High mobility group box 1) While HMGb1 is involved in inflammatory responses, it is not classified as a PAMP associated with pathogens, rather functioning in damage and stress signaling.
D: Peptidoglycan Peptidoglycan serves as a PAMP in bacterial cell walls but does not relate to viral pathogens, thus lacking relevance to the context of viral RNA recognition by the immune system.
Which of the following best describes complementary system
Rationale:
A: A group of carbohydrates and lipids that circulate in the blood and a part of immune system. This description conflates different biological components, as the complementary system primarily consists of proteins rather than carbohydrates or lipids.
C: Always activated proteins circulate in blood. Complementary proteins are not continuously active; they require specific triggers for activation, which distinguishes them from a state of constant circulation.
D: None of the above. This option dismisses the accurate description provided in option B, which correctly identifies the complementary system's primary function and components related to opsonization and inflammatory responses.
Macrophages recognize microorganisms through the Interaction of their substances with what receptor?
Rationale:
Macrophages recognize microorganisms through the interaction of their substances with PRR. These pattern recognition receptors play a crucial role in identifying pathogen-associated molecular patterns, enabling macrophages to initiate immune responses effectively.
A: antigen receptor Antigen receptors are specific to lymphocytes and primarily recognize unique antigens, not broad pathogen patterns, limiting their role in macrophage recognition of microorganisms.
B: complement receptor Complement receptors facilitate opsonization but do not directly engage with microorganisms; they assist in enhancing phagocytosis rather than recognizing pathogens independently.
C: membrane IG Membrane immunoglobulin is primarily associated with B cells, focusing on specific antigens rather than the broader recognition function performed by PRRs in macrophages.
A 66-year-old man with advanced pancreatic cancer develops cachexia (loss of mass) Which cytokine is primarily responsible for the cachexia seen in certain patients with cancer or debilitating infections?
Rationale:
Tumor necrosis factor is primarily responsible for the cachexia observed in patients with advanced cancer. This cytokine contributes to metabolic changes, promoting muscle wasting and fat loss, which are characteristic of cachexia in these patients.
A: Interferon-α This cytokine is involved in immune responses but does not play a primary role in the muscle wasting associated with cachexia in cancer patients.
B: Interleukin-7 While important for lymphocyte development, interleukin-7 does not directly influence the metabolic processes leading to cachexia in cancer or debilitating infections.
C: Interleukin-17 This cytokine is primarily linked to inflammatory responses and autoimmune conditions, lacking a direct connection to the muscle and fat loss seen in cachexia.
Which of the following peripheral immune tissues is likely to be different from teen through life to old age?
Rationale:
C: thymus
The thymus undergoes significant changes throughout life, particularly in its size and function. In childhood, it is active in T-cell maturation, but it gradually involutes with age, leading to decreased immune response capabilities in older adults.
A: spleen
The spleen maintains a relatively stable structure and function throughout life, continuing to filter blood and support immune responses without significant age-related changes in its primary roles.
B: MALTs
Mucosa-associated lymphoid tissues (MALTs) remain functional across various life stages, adapting to environmental antigens but not exhibiting drastic transformations or declines directly attributed to aging.
D: lymph nodes
Lymph nodes continue to play a crucial role in immune response throughout life, effectively filtering lymph and responding to pathogens without marked alterations as one ages.
Which of the following statements is TRUE regarding diurnal variation of the absolute eosinophil count (AEC)?
Rationale:
Diurnal variation of the absolute eosinophil count (AEC) is lower in the early morning.
Eosinophil levels fluctuate throughout the day, typically reaching their lowest point in the early hours, which aligns with the body's circadian rhythms and patterns of immune function. This decline may influence various physiological processes, including responses to allergens and inflammation, thereby impacting overall health and disease susceptibility.
A: higher in the evening. Eosinophil counts generally increase later in the day, contrary to this statement, making evening levels typically elevated rather than lower than morning counts.
B: lower in the afternoon. The AEC typically rises by afternoon, contradicting this option, as immune responses are often heightened during this time, reflecting increased eosinophil activity.
C: higher in the afternoon. This statement misrepresents the expected trend, as AEC is known to rise during the day, but not specifically peak in the afternoon compared to morning levels.
The diagnosis of chronic granulomatous disease CGD is MOST often made by
Rationale:
The diagnosis of chronic granulomatous disease (CGD) is most often made by the nitroblue tetrazolium dye test. This test effectively assesses the ability of neutrophils to produce reactive oxygen species, a crucial function impaired in CGD patients, thereby confirming the diagnosis through observable results in the patient's immune response.
A: DNA analysis This method identifies genetic mutations but is not the primary diagnostic tool for CGD, as functional assays provide more immediate insights into neutrophil activity.
B: flow cytometry This technique analyzes cell populations and can detect certain immune deficiencies, yet it does not specifically target the oxidative burst defect characteristic of CGD.
C: neutrophil G6PD assay This assay evaluates glucose-6-phosphate dehydrogenase activity, which relates to other conditions but does not directly assess the oxidative burst functionality essential for diagnosing CGD.
Which of the following components of the innate immune system involves recognition molecules such as mannan-binding lectin (MBL) for bacteria with mannose on the surface?
Rationale:
B: The complement system involves recognition molecules like mannan-binding lectin (MBL) that specifically identify and bind to mannose on bacterial surfaces, facilitating opsonization and subsequent immune responses against pathogens.
A: Natural killer (NK) cells Primarily target and destroy infected or cancerous cells through direct cytotoxicity rather than utilizing recognition molecules like MBL for pathogen identification.
C: Oxygen dependent and independent killing Refers to mechanisms of microbial destruction within immune cells, lacking specific recognition features such as MBL, which are crucial for identifying pathogens.
D: Interferons Function primarily in signaling and antiviral responses rather than engaging in direct recognition of bacteria. They do not involve MBL or similar molecules for pathogen targeting.
Eventual elimination of antigen
Rationale:
Eventual elimination of antigen occurs during the effector phase. This phase is characterized by the activation and execution of immune responses that effectively target and eliminate pathogens, ensuring the body's defense mechanisms function optimally.
A: Cognitive phase This phase focuses on recognizing antigens and generating an appropriate immune response, rather than the direct elimination of the antigen itself, which happens later.
B: Activation phase Although this phase involves stimulating immune cells, it primarily centers on preparing the immune system to respond, not on the direct eradication of antigens.
D: None of the above This option dismisses the specific phases of the immune response that directly contribute to antigen elimination, thus overlooking the essential roles they play in immunity.
Given that an individual's parents have completely different HLA genes, that individual will have about different class I and II MHC molecules on the surface of certain of their lymphoid cells.
Rationale:
D: An individual with parents having completely different HLA genes can inherit a combination of alleles from each parent, resulting in a total of 12 different class I and II MHC molecules on their lymphoid cells. This diverse genetic background allows for a wide array of immune responses.
A: 3 Only one allele from each parent would produce a limited number of MHC molecules, failing to account for the genetic diversity present in a typical individual.
B: 6 This option suggests a minimal variation, which neglects the significant contribution of both parents' distinct HLA genes that facilitate a larger array of MHC molecules.
C: 9 While this indicates some diversity, it underestimates the full potential of class I and II MHC molecule combinations derived from two completely different parental HLA genes.
Has different subtypes
Rationale:
IgG has different subtypes. IgG comprises four distinct subclasses: IgG1, IgG2, IgG3, and IgG4, each playing unique roles in immune responses, allowing for specialized functions and adaptability to various pathogens.
B: IgE primarily functions in allergic responses and defense against parasites, lacking distinct subtypes. Its singular focus limits its classification compared to the versatile IgG, which has multiple subclasses.
C: IgM serves as the first antibody produced during an immune response and does not have recognized subtypes. Its primary role in initial defense contrasts with the varied subtypes of IgG.
D: IgG & IgM combines two antibody types, but IgM lacks subtypes. While both are crucial for immunity, only IgG demonstrates the diversity of subtypes required for specialized immune functions.
Each polypeptide chain (heavy and light) on immunoglobulin has a variable (V) and constant (C) region. Immunoglobulin chains are encoded by that is/are rearranged during development to assemble a functional gene encoding either a heavy or a light chain.
Rationale:
Sets of gene segments; B cell. Immunoglobulin chains are uniquely assembled through the rearrangement of specific gene segments during B cell development, allowing for the creation of diverse heavy and light chains essential for immune function.
A: A single continuous DNA sequence; B cell. A continuous sequence fails to account for the necessary rearrangement of distinct gene segments essential for generating diverse immunoglobulin chains in B cells.
B: A single continuous DNA sequence; T cell. T cells do not utilize a continuous DNA sequence for their receptors; they also rely on gene segment rearrangement, similar to B cells, for diversity.
D: Sets of gene segments; T cell. While T cells do rearrange gene segments, the question specifically pertains to immunoglobulins, which are exclusively associated with B cells and their development.
Which of the following TCR genetic chains contain D-segments, similar to immunoglobulin heavy chains?
Rationale:
C: Beta (β); Delta (δ) contain D-segments, paralleling the structure of immunoglobulin heavy chains, which consist of variable and constant regions including D-segments crucial for diversity in antigen recognition.
A: Alpha (α); Beta (β) lacks D-segments in the alpha chain, which is similar to immunoglobulin light chains, thereby not exhibiting the same complexity in segment composition as heavy chains.
B: Delta (δ); Gamma (γ) do not include D-segments in their genetic structure, causing them to differ significantly from immunoglobulin heavy chains, which rely on D-segment diversity for functionality.
D: Gamma (γ); Alpha (α) do not possess D-segments, which limits their structural similarity to immunoglobulin heavy chains, as these chains require D-segments for generating extensive diversity in immune responses.
Class III MHC genes encode for which of the following?
Rationale:
Class III MHC genes encode for complement molecules. These genes play a crucial role in the immune system by producing proteins that aid in the opsonization and clearance of pathogens, enhancing immune response.
A: CD4+ T cells This option misrepresents the function of Class III MHC genes, which do not directly encode for T cell types but rather for complement proteins involved in immune processes.
B: CD8+ T cells Similar to CD4+ T cells, this option incorrectly attributes the encoding function of Class III MHC genes to T cell types instead of the complement system.
D: Cytokine molecules Class III MHC genes are not responsible for encoding cytokines; they primarily produce complement proteins, which are distinct from the signaling molecules involved in immune communication.
Directly: some recognize nonpeptide phosphorylated lipids and carbohydrates; other recognize antigen that have not been processed
Rationale:
Some recognize nonpeptide phosphorylated lipids and carbohydrates; other recognize antigen that have not been processed.
TCR γδ specifically identifies these unique antigens, enabling immune responses against a broader spectrum of pathogens. This receptor plays a crucial role in recognizing nonpeptide antigens, distinguishing it from other T cell receptors that primarily target processed peptides.
A: Immunoglobulin binds to processed antigens presented by MHC molecules, focusing on peptide recognition rather than the broader spectrum that TCR γδ addresses.
B: TCRαβ primarily recognizes peptide antigens presented by MHC class I and II, limiting its scope compared to TCR γδ, which engages with nonpeptide antigens.
D: None of the above does not apply, as TCR γδ specifically fulfills the criteria of recognizing nonpeptide phosphorylated lipids and unprocessed antigens, making it a valid choice.
Protein antigens bound to complement component C3d can bind simultaneously to both and the BCR. This enables the co-receptor complex to cluster and crosslink with the BCR, inducing phosphorylation.
Rationale:
C: Protein antigens bound to complement component C3d specifically interact with CD21, facilitating the clustering of the co-receptor complex with the BCR. This crosslinking is crucial for activating B cells and enhancing immune responses.
A: CD19 functions as a signaling molecule but does not directly bind to C3d, limiting its role in this specific antigen recognition process.
B: CD20 primarily serves as a marker for B cells and does not participate in binding C3d, thus lacking involvement in the described co-receptor complex activation.
D: CD81 acts as a co-receptor for various immune receptors but does not directly interact with C3d, making it ineffective in the context of B cell activation through this mechanism.
In the embryonic human, the primary lymphoid organs are initially in the yolk sac, then in the fetal , and finally in the
Rationale:
In the embryonic human, the primary lymphoid organs are initially in the yolk sac, then in the fetal liver, and finally in the bone marrow and thymus.
The liver serves as a key site for hematopoiesis during fetal development, providing a crucial environment for the maturation of immune cells, while the bone marrow ultimately becomes the primary site for blood cell production.
A: Spleen and kidneys; The kidneys do not play a significant role in lymphoid organ development during embryogenesis, focusing instead on other functions unrelated to lymphocyte maturation.
B: Spleen and thymus; The thymus is involved in T-cell development, but the spleen does not serve as a primary lymphoid organ in the embryonic stage, which is misleading.
C: Kidneys and thymus; While the thymus is essential for T-cell maturation, the kidneys are not involved in the formation of primary lymphoid organs during embryonic development.
Which of the following has the surface marker CD34 instead of the surface marker CD19, during B cell development?
Rationale:
Stem cells express the surface marker CD34 during the early stages of B cell development. This marker is characteristic of hematopoietic stem cells, indicating their potential to differentiate into various blood cell types, including B cells.
B: Pro-B cell Pro-B cells begin to express CD19, indicating their progression in B cell development and loss of CD34 expression, marking a shift in their differentiation potential.
C: Early pre-B cell Early pre-B cells transition further along the developmental pathway and predominantly express CD19, signifying their maturation away from the stem cell stage where CD34 is present.
D: Late pre-B cell Late pre-B cells also express CD19, reflecting their advanced differentiation status, further indicating that CD34 is absent as they prepare for full B cell functionality.
Where are double-positive (DP) cells found?
Rationale:
Double-positive (DP) cells are found in the thymus cortex. This region is crucial for the maturation process of T cells, where DP cells undergo selection to ensure proper immune function before entering circulation.
A: Bone marrow DP cells are not located in the bone marrow, as this area primarily produces hematopoietic stem cells and other progenitor cells rather than mature T cell forms.
B: Thymus subcapsular zone This area is primarily involved in the early stages of T cell development, where thymocytes undergo initial differentiation before progressing to the cortex for further maturation.
D: Thymus medulla The medulla is mainly responsible for the final maturation and selection of T cells, not where double-positive cells are actively generated or predominantly found.
T cell activation of TH1 leads to ___ antibody production and opsonization (or macrophage activation). Activation of TH2 leads to ___ antibody production and activation of mast cells and eosinophils.
Rationale:
TH1 leads to IgG antibody production and opsonization, while TH2 activates mast cells and eosinophils, resulting in IgE antibody production. This reflects the distinct roles these T helper cell subsets play in immune responses.
A: CD4+; IgE; IgG. Although CD4+ T cells are involved, TH1 produces IgG, not IgE, and TH2 primarily produces IgE.
C: CD8+; IgE; IgG. CD8+ T cells are cytotoxic and do not primarily drive antibody responses; TH1 and TH2 are responsible for IgG and IgE production, respectively.
D: CD8+; IgG; IgE. The role of CD8+ is not associated with antibody production; TH1 and TH2 cells, not CD8+, mediate IgG and IgE responses.
Which of the following is NOT true regarding interferon?
Rationale:
Interferon is not associated with the inactivation of antigen-presenting cells. Instead, it enhances their function, promoting an effective immune response against infections by facilitating antigen presentation.
A: Interferon prevents infection spreading from cell to cell. This statement highlights interferon's role in inhibiting viral replication and spread, thereby limiting the infection's progression within the host.
B: NK cells are activated by interferon and lyse infected cells. This accurately describes interferon's function, as it stimulates natural killer cells to target and destroy cells that harbor viruses.
D: Interferon is viral specific, attacking viral proteins. This misrepresents interferon's action, as it possesses a broader mechanism that activates various immune responses rather than selectively targeting specific viral proteins.
What is the primary response seen in acute-phase responses to infection?
Rationale:
Increased body temperature. This response is a hallmark of acute-phase reactions to infection, as the body elevates its temperature to create an environment less favorable for pathogens, enhancing immune function and promoting healing.
A: Decreased blood pH. During acute infections, blood pH typically remains stable or may even increase rather than decrease, as the body actively manages metabolic processes to combat pathogens.
B: Decreased metabolic pH. Metabolic pH generally does not decrease during infections; instead, metabolic reactions often accelerate to support immune responses, potentially causing a rise in pH levels.
D: Increased heart rate. While heart rate may increase in response to infection, it is not the primary acute-phase response, as the body prioritizes temperature elevation for effective pathogen defense.
Degrade host cell proteins, activate caspase enzyme system
Rationale:
Degrade host cell proteins, activate caspase enzyme system.
Granzyme functions as a serine protease, entering target cells via perforin-created pores. Once inside, it cleaves specific host proteins, triggering apoptosis through the activation of caspase enzymes, leading to cell death.
A: Perforin Creates pores in target cell membranes but does not directly degrade proteins or activate caspases, merely facilitating granzyme entry.
C: Fas ligand Engages death receptors on target cells to induce apoptosis but does not degrade proteins or activate the caspase system directly.
D: None of the above Suggests that no options relate to the question, overlooking granzyme's critical role in apoptosis through protein degradation and caspase activation.
A patient presents in the winter months with swollen lips. The patient says they forgot their lip balm. Uncontrolled activation of the classical complement pathway is responsible for the swelling. Records show the patient has a C1 inh deficiency. Which of the following does this patient have?
Rationale:
Hereditary angioedema is the condition this patient has. The context indicates swelling of the lips due to uncontrolled activation of the classical complement pathway, which is characteristic of C1 inhibitor deficiency linked to hereditary angioedema.
A: C5-C9 deficiency results in a lack of membrane attack complex formation, leading to susceptibility to certain infections, not lip swelling.
B: Glucose-6-phosphate dehydrogenase deficiency primarily affects red blood cell integrity, causing hemolysis under specific stressors, not causing localized swelling of the lips.
D: Severe combined immunodeficiency disease (SCID) involves severe immune dysfunction, leading to heightened infection risk, but does not present with acute swelling like hereditary angioedema does.