Biology Test Immunology 5

Question 1

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

Accepted Answer

IgM

Answer

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

Question 2

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

Accepted Answer

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

Answer

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.

Question 3

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

Accepted Answer

IL-4

Answer

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

Question 4

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

Accepted Answer

Severe combined immunodeficiency (SCID)

Answer

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).

Question 5

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

Accepted Answer

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

Answer

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.

Biology Practice Test

Biology Practice Test

Biology Test Immunology 5