Immune System
Which is not an antigen-presenting cell (or APC)?

B cell
Polymorphonuclear leukocyte (or PMN)
Dendritic cell
All of these

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Immune System
Numerous antibodies can be prepared, against one antigen, each binds to unique epitopes. How is this antibody diversity generated?

Antibody proteins can physically change their shape to bind different epitopes
By rearrangements of the DNA encoding the variable regions of the heavy and light chains
Both (a) and (b)
By the combination of different heavy and light chains that form the antigen binding site

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