ok, BIG POINT:
You have to understand the basics of activation. IF say an antigen presenting cell (Dendrocyte, B-cell, Macrophage) [T-CELL ARE NOT ANTIGEN PRESENTING!!!!], binds an antigen (virus), then CROSSLINKING occurs and the cell gobbles up antigen and then PRESENTS IT ON THE SURFACE. A lot of you know that, but THEN you must follow the storyline. And lovely young helper T cell comes along and attaches or holds hands with the antigen presenting cell. THEN, the T-helper cell "blushes red" and is so happy she throws out IL-2, IL-4, and IL-5 that stimulate both B-cells and T-cells (IL-2 here). Some of the activated B-cells from what kind of cells in the secondary response and what is the most common surface Ig?