Mcq_sem3_mini1 Innate Defenses, Complement, Antigen And Antibody Structure And Function

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Quizzes Created: 32 | Total Attempts: 36,280
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Questions and Answers
  • 1. 

    Innate defenses, Complement, Antigen and antibody structure and function Toll-like receptors (TLR) are important activators of the innate immune system. Which of the following microbial substances activates TLR-4?

    • A.

      Peptidoglycan

    • B.

      Lipopolysaccaride

    • C.

      Double stranded RNA

    • D.

      Bacterial flagella

    • E.

      Single stranded RNA

    Correct Answer
    B. Lipopolysaccaride
    Explanation
    TLR-4 is specifically activated by lipopolysaccharide (LPS), which is a component of the outer membrane of Gram-negative bacteria. LPS is recognized by TLR-4 and triggers an immune response, leading to the activation of innate defenses. Peptidoglycan is recognized by other TLRs, such as TLR-2, and activates a different pathway. Double stranded RNA is recognized by TLR-3, while single stranded RNA is recognized by TLR-7 and TLR-8. Bacterial flagella do not directly activate TLR-4.

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  • 2. 

    Patients with Leukocyte adhesion deficiency syndrome (LAD) are unable to produce the beta chain of the complement receptor 3 (CR3) heterodimer. Which of the following functions may be deficient in LAD patients?

    • A.

      Lysis of bacteria

    • B.

      Opsonization of bacteria

    • C.

      Leukocyte chemotaxis

    • D.

      Neutrophil diapedesis

    • E.

      Macrophage activation

    Correct Answer
    B. Opsonization of bacteria
    Explanation
    Patients with Leukocyte adhesion deficiency syndrome (LAD) are unable to produce the beta chain of the complement receptor 3 (CR3) heterodimer. Opsonization is the process of marking bacteria for phagocytosis by immune cells. Since LAD patients cannot produce the beta chain of CR3, which is involved in opsonization, their ability to opsonize bacteria may be deficient. This means that LAD patients may have difficulty in effectively marking bacteria for phagocytosis, leading to impaired immune response against bacterial infections.

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  • 3. 

    The activity of complement is dependent on the sequential activation of its components in a cascading fashion. Which of the complement activation pathways would be most severely affected by a defect in the synthesis of Factor D?

    • A.

      The alternate pathway

    • B.

      The classical pathway

    • C.

      The lectin pathway

    • D.

      None of the pathway would be affected

    Correct Answer
    A. The alternate pathway
    Explanation
    A defect in the synthesis of Factor D would most severely affect the alternate pathway of complement activation. Factor D is a crucial component in the alternate pathway, as it cleaves Factor B to generate the active fragment, which then combines with C3b to form the C3 convertase enzyme. Without Factor D, the alternate pathway cannot proceed, leading to a significant impairment in the activation of complement.

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  • 4. 

    A 70-year-old man is admitted to the hospital for recurrent lung infections with Streptococcus pneumonae. He has a history of chronic alcoholism and a 100 pack year smoking history. Extensive laboratory testing reveals that he cannot activate the alternate pathway of complement. A lung biopsy reveals numerous bacteria, but few leukocytes in the lung. Which of the following mediators is Most Likely deficient?

    • A.

      C3b

    • B.

      C4a

    • C.

      C5a

    • D.

      C6

    • E.

      Membrane attack complex

    Correct Answer
    C. C5a
    Explanation
    The patient's inability to activate the alternate pathway of complement suggests a deficiency in one of the mediators involved in this pathway. C5a is a potent chemotactic factor that attracts and activates neutrophils, which are responsible for phagocytosing bacteria. Therefore, a deficiency in C5a is the most likely explanation for the few leukocytes seen in the lung biopsy despite the presence of numerous bacteria.

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  • 5. 

    The complement cascade can be activated in a number of ways. Cobra venom factor (CVF) is one of these ways. Which pathway is activated by CVF?

    • A.

      The lectin pathway

    • B.

      The alternative pathway

    • C.

      The classical pathway

    • D.

      Both the lectin and the classical pathway

    Correct Answer
    B. The alternative pathway
    Explanation
    The alternative pathway is activated by cobra venom factor (CVF). The alternative pathway is one of the three pathways of the complement cascade, along with the classical pathway and the lectin pathway. CVF specifically activates the alternative pathway, leading to the activation of complement proteins and the initiation of an immune response.

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  • 6. 

    A 23 year old female patient presents with a malar rash, joint pains and general malaise. Laboratory tests indicated the presence of anti-Sm and anti-ds DNA antibodies. If you were to measure the patients complement C2 and C4 levels, what might you expect?

    • A.

      C4 and C2 would be lower than the normal range

    • B.

      C2 and C4 would be higher than the normal range

    • C.

      C2 would be higher and C4 lower than the normal range

    • D.

      C2 would be lower and C4 higher than the normal range

    Correct Answer
    A. C4 and C2 would be lower than the normal range
    Explanation
    The presence of anti-Sm and anti-ds DNA antibodies, along with symptoms such as malar rash, joint pains, and general malaise, suggests a possible diagnosis of systemic lupus erythematosus (SLE). In SLE, there is often complement activation and consumption, leading to decreased levels of complement proteins such as C2 and C4. Therefore, it would be expected that C4 and C2 levels would be lower than the normal range in this patient.

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  • 7. 

    In complement activation, the mannan binding lectin (MBL) pathway is characterized by which of the following?

    • A.

      ML is synthesized by the liver when stimulated by IL-2

    • B.

      MEL acts on Cl to produce C4b and C4a

    • C.

      MBL acts on C3 to produce C3b and C3a

    • D.

      MBL is important in controlling infection after the classical pathway is activated

    Correct Answer
    B. MEL acts on Cl to produce C4b and C4a
  • 8. 

    Which of the following immunoglobulin regions/domains determine the affinity, specificity and idiotype of the molecule?

    • A.

      The light chain hypervariable and constant domains

    • B.

      The light and heavy chain hypervariable and constant domains.

    • C.

      The light and heavy chain hypervariable domains

    • D.

      The light chain hypervariable domains

    • E.

      The light and heavy chain framework domains

    Correct Answer
    C. The light and heavy chain hypervariable domains
    Explanation
    The light and heavy chain hypervariable domains determine the affinity, specificity, and idiotype of the immunoglobulin molecule. These domains contain the most variable regions within the immunoglobulin molecule, allowing for a wide range of antigen recognition and binding. The hypervariable domains contribute to the diversity of immunoglobulin molecules and their ability to recognize and bind to specific antigens.

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  • 9. 

    V(D)) recombination events take place in the following cells

    • A.

      Natural killer cells, B cells & neutrophils

    • B.

      Eosinophils, T cells & B cells

    • C.

      B cells, denclritic cells & T cells

    • D.

      Plasma cells, mast cells ar, B cells

    • E.

      CD4+ T cells, CD8+ T cells & B cells

    Correct Answer
    E. CD4+ T cells, CD8+ T cells & B cells
    Explanation
    The correct answer is CD4+ T cells, CD8+ T cells & B cells. V(D)J recombination is a process that occurs during the development of lymphocytes, specifically T cells and B cells. This process involves the rearrangement of gene segments called V (variable), D (diversity), and J (joining) to generate a diverse repertoire of antigen receptors. CD4+ T cells, CD8+ T cells, and B cells are all types of lymphocytes that undergo V(D)J recombination. This process is essential for the immune system to recognize and respond to a wide range of pathogens.

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  • 10. 

    A single patient that produces IgG1 to differing epitopes will have which of the following?

    • A.

      Same isotype, same allotype, same idiotype

    • B.

      Same isotype, different allotype and different idiotype

    • C.

      Same isotype, different allotype, same idiotype

    • D.

      Different isotype, different allotype, different idiotype

    • E.

      Same isotype, same allotype, different idiotype

    Correct Answer
    E. Same isotype, same allotype, different idiotype
    Explanation
    A single patient that produces IgG1 to differing epitopes will have the same isotype (IgG1), indicating that the antibodies belong to the same class of immunoglobulins. They will also have the same allotype, meaning that they share the same genetic variants of the constant region of the antibody. However, they will have different idiotype, which refers to the unique combination of variable regions that determine the specificity of the antibody.

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  • 11. 

    In 1972 Rodney Porter won the Nobel Prize for demonstrating the structure of antibodies, He digested IgG using papain to produce what?

    • A.

      One F(abi)2 plus some small fragments

    • B.

      2 Fab plus one Fc

    • C.

      2 Fc plus one Fab

    • D.

      One F(ab')2 plus one Fc

    Correct Answer
    B. 2 Fab plus one Fc
    Explanation
    Rodney Porter won the Nobel Prize in 1972 for his work on the structure of antibodies. He used papain to digest IgG, which resulted in the production of 2 Fab fragments and one Fc fragment. The Fab fragments are responsible for binding to antigens, while the Fc fragment is involved in various immune functions. This digestion process allowed Porter to better understand the structure and function of antibodies.

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  • 12. 

    Antibodies of different classes, including IgM, IgG, IgA, and IgE, arise after varying kinds of antigenic stimulation. In which of the following situations would particular antibody responses be expected?

    • A.

      Antigens such as polysaccharides give rise to T cell-dependent responses resuting in mostly IgG

    • B.

      Antigens such as proteins give rise to T dell-independent responses resulting in mostly IgM

    • C.

      IgM produced after exposure to a carbohydrate antigen will have relatively low affinity for its antigen

    • D.

      When antigen is presented at MUCOS3i surfaces, IgE is likely to be the main antibody secreted at the surface

    Correct Answer
    C. IgM produced after exposure to a carbohydrate antigen will have relatively low affinity for its antigen
    Explanation
    When exposed to a carbohydrate antigen, the IgM antibodies produced will have relatively low affinity for the antigen. This is because carbohydrate antigens are typically T cell-independent antigens, meaning they do not require T cell help for their immune response. T cell-independent antigens stimulate B cells to produce IgM antibodies directly, without the need for affinity maturation. As a result, the IgM antibodies produced in response to carbohydrate antigens will have lower affinity compared to antibodies produced in response to protein antigens, which require T cell help and undergo affinity maturation to produce higher affinity antibodies such as IgG.

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  • 13. 

    IgM differs from igG in a number of ways, but which of the following differences between IgG and 1gM would you agree with?

    • A.

      IgM is almost always low affinity for antigen, while IgG is usually high affinity for antigen.

    • B.

      IgM, but not IgG can bind to soluble antigens

    • C.

      Certain subtypes of IgG, can activate complement, but 1gM can almost never activate complement by the classical pathway.

    • D.

      Both IgN1 and IgG are produced subsequent to somatic hypermutabon of SCR genes. innate defenses, Cdrnplernent, Antigen and antibody structure and function

    Correct Answer
    A. IgM is almost always low affinity for antigen, while IgG is usually high affinity for antigen.
    Explanation
    IgM is almost always low affinity for antigen, while IgG is usually high affinity for antigen. This means that IgM antibodies have a weaker binding to antigens compared to IgG antibodies. IgM is the first antibody produced during an immune response and is responsible for the initial defense against pathogens. It has a pentameric structure which allows it to bind to multiple antigens simultaneously. On the other hand, IgG antibodies are produced later in the immune response and have a higher affinity for antigens, providing a stronger and more specific immune response.

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