Q. Which class of immunoglobulin is the first to be produced in response to an infection?

Correct Answer: a) IgM

Explanation:
– In a primary immune response, naive B cells initially produce and secrete IgM because they first express membrane-bound IgM (and IgD).
– Only later, with T-cell help, do B cells undergo class-switch recombination to produce other antibodies like IgG, IgA, or IgE.
– IgM is typically a pentamer, giving it high avidity and making it very effective at early neutralization and complement activation.