Studies on Fc receptor function: II. Depressive effect of aggregated IgG2b on B lymphocyte activation by T-dependent and T-independent antigens

Abstract

Mouse aggregated IgG2b, continuously present in mouse spleen cell cultures, markedly depressed, in a dose-dependent fashion, the direct plaque-forming cell response to sheep red blood cells (SRBC, T-dependent) and to DNP-Ficoll (T-independent). Pretreatment of mouse spleen cells with IgG2b for 30 min at 4 °C prior to culturing also markedly depressed the response to both antigens. Delayed addition of IgG2b to SRBC-immunized cultures caused an early and a late depression separated by a period when no significant depression was seen. Using DNP-Ficoll as antigen the late-occurring depression was observed only in Mishell-Dutton cultures, while it was not seen in microcultures. These data support a regulatory role of Fc receptors on the activation of B lymphocytes by antigens and suggest that Fc receptors may be important in at least two events during the differentiation of B lymphocytes into plasma cells: an early, short lived one and a later, longer-lasting event.