Molecular, Cellular and Systemic Mechanisms for Regulating IgCH Expression

IgCH expression changes dramatically at several points along the antigentriggered developmental pathway from "virgin" B to mature IgG-secreting (plasma) cells. IgD and igM receptors are present on the virgin B cell and are still expressed on "early" memory cells. But the expression of these receptors terminates when early memory cells are triggered to differentiate to the "mature" memory cells (present in animals primed with hapten-carrier conjugates on alum or in other adjuvants). The expression of IgG receptors, in contrast, apparently begins when virgin cells differentiate into early memory cells and it continues thereafter. Thus, by the time B cells reach the mature memory stage, they have lost IgD and IgM and, instead, carry surface IgG molecules that indicate the antibody-secretion committment of the cell (see Figure 1 and Herzenberg et al. 1980a, Black et al. 1977, 1980, Okumura et al. 1976, Coffman & Cohen 1977. Abney et al. 1978).