THE ROLES OF GAMMA-1 HEAVY-CHAIN MEMBRANE EXPRESSION AND CYTOPLASMIC TAIL IN IGG1 RESPONSES

In antibody responses, B cells switch from the expression of immunoglo bulin (Ig) mu and delta heavy (H) chains to that of other Ig classes ( alpha, gamma, or epsilon), each with a distinct effector function. Mem brane-bound forms of alpha, gamma, and epsilon, but not mu and delta, have highly conserved cytoplasmic tails. Mutant mice unable to express membrane gamma 1 H chains or producing tailless gamma 1 H chains fail ed to generate efficient IgG1 responses and IgG1 memory. H chain membr ane expression after class switching is thus required for these functi ons, and class switching equips the B cell antigen receptor with a reg ulatory cytoplasmic tail that naive B cells lack.