IMMUNOGLOBULIN ISOTYPE REGULATION BY ANTIGEN-PRESENTING CELLS IN-VIVO

The isotype and magnitude of the B cell response clearly depends on th e in vivo activation of T helper (Th) cells which secrete different ly mphokines. Since Th are activated by the presentation of the antigen o n specialized cells, we wished to test whether the nature of the antig en-presenting cells (APC) influences the isotypic profile of the humor al response. Data are presented showing that antigen-pulsed dendritic cells (DC) and peritoneal macrophages induce the synthesis of specific antibodies when injected in syngeneic animals. By contrast, a single injection of antigen-pulsed resting B cells does not prime the mice in vivo. Moreover, the injection of antigen-pulsed DC induces the synthe sis of specific IgG2a and IgG1 antibodies, whereas peritoneal macropha ges favor the production of IgG1 and IgE antibodies specific for the a ntigen. These data show that the isotype and the amplitude of the B ce ll response can be regulated by the nature of the APC, and indirectly suggest that Th cell differentiation is controlled at the level of ant igen presentation.