The variable region also contains a heavy and a light chain. The antigen-binding site is on the variable region. This allows for lock and key binding between the antigen and the antibody. Immunological Memory Immunological memory is due to clonal expansion. A virgin B cell is first exposed to the antigen.
Memory cells produce more memory cells.
After the second exposure, more active and memory cells are produced by the memory cells. This is the reason why it usually takes about two weeks before you get over a flu, but it takes a shorter time to get well after the second exposure. By the time the flu virus hits again, you would have enough memory cells in your body that crank out memory and active cells capable of producing millions of antibodies. You get sick from flu the following year again because the next time, it would be a different, mutated virus. T cells - T cells don't produce antibodies, therefore, they don't have as much endoplasmic reticulum as B cells do.