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Which antibody isotype is the first antibody produced by B cells upon initial encounter with an antigen?

A. IgA
B. IgD
C. IgE
D. IgG
E. IgM

1 Answer

3 votes

Final answer:

IgM is the first antibody produced by B cells upon initial encounter with an antigen.

Step-by-step explanation:

IgM is the first antibody produced by B cells upon initial encounter with an antigen. It is initially produced in a monomeric membrane-bound form that serves as an antigen-binding receptor on B cells. The secreted form of IgM assembles into a pentamer with five monomers of IgM bound together by a protein structure called the J chain. IgM is important during the primary and secondary immune responses and can be used as a diagnostic marker for active or recent infections.

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