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Immunology Flashcards

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  1. Which immunoglobulin isotype is the first produced during a primary immune response?

    Answer: IgM

    IgM is the first antibody isotype produced during a primary immune response because it does not require class-switch recombination.

  2. What is the primary mechanism by which NK (natural killer) cells recognize and kill target cells?

    Answer: Detecting absence of MHC class I ('missing self')

    NK cells use inhibitory receptors that recognize MHC class I; when a cell downregulates MHC class I (as many viruses and tumors do), NK cells detect 'missing self' and kill the target.

  3. Which cytokine produced by Th2 cells is critical for driving IgE class switching in B cells?

    Answer: IL-4

    IL-4 (along with IL-13) signals B cells to undergo class-switch recombination to produce IgE, which is central to allergic responses.

  4. A newborn is found to lack both T and B lymphocytes. Which condition does this most likely represent?

    Answer: Severe combined immunodeficiency (SCID)

    SCID is characterized by the absence of functional T and B lymphocytes, often due to mutations in genes like IL-2Rγ (γc chain) or ADA (adenosine deaminase).

  5. What is the function of the neonatal Fc receptor (FcRn) in humoral immunity?

    Answer: It rescues IgG from lysosomal degradation and transports IgG across the placenta

    FcRn extends the half-life of IgG by rescuing it from degradation and also transfers maternal IgG across the placenta to provide passive immunity to the fetus.

  6. Which vaccine adjuvant mechanism enhances adaptive immune responses by activating the NLRP3 inflammasome?

    Answer: Alum (aluminum salts)

    Alum activates the NLRP3 inflammasome in macrophages and dendritic cells, promoting IL-1β release and enhancing adaptive immune priming.

  7. Which process allows a single B cell to produce antibodies with different isotypes (e.g., IgM → IgG) while maintaining the same antigen specificity?

    Answer: Class-switch recombination

    Class-switch recombination (CSR) changes the constant region of the heavy chain, allowing B cells to switch from IgM to IgG, IgA, or IgE while retaining the same variable region and antigen specificity.