Immunological properties of Fc receptor on lymphocytes: 2. Differentiation from FcR − to FcR + cells and their functional differences in in vitro antibody response

Abstract

In in vitro plaque-forming cell (PFC) response to particulate as well as to soluble antigen, the functional difference between Fc receptor-bearing (FcR +) and nonbearing (FcR −) murine splenic lymphocytes was analyzed using the EA rosetting method. In the secondary anti-horse red blood cell (HRBC) response of C3H mice, FcR − cells showed higher IgM and IgG responses than did FcR + cells. When nylon wool (NW)-purified T cells primed with keyhole limpet hemocyanin (KLH) were fractionated into FcR − and FcR + T cells, helper activity was proven in the former subset in the cooperation with syngeneic spleen cells primed with dinitrophenylated ascaris extract (DNP-Asc). FcR + T cells showed essentially no helper activity. When FcR − cells were cultured, neogenesis of FcR + cells was observed on Days 3 to 5. The conversion from FcR − to FcR + cells was prominent in B cells (40 to 50%), whereas NW-purified nonadherent FcR − T cells converted poorly (15 to 20%). The converting process was accelerated slightly by mitogens, but was least affected by antigens. To examine the possible contribution of neogeneic FcR + T cells in the helper activity, KLH-primed FcR − T cells were precultured for 7 days with homologous antigen. The specific helper activity of the cultured T cells proved to be unaffected by the depletion of neogeneic FcR + T cells by EA rosetting. The neogeneic FcR + T cells had no helper activity. It was thus suggested that helper T cells remain in the FcR − cell fraction and do not convert to the FcR + state during the cooperating process.