γ-Globulin and Antibody Formation <i>in Vitro</i>

Abstract

Summary The spleens of rabbits, injected either with 10 mg of BGG intravenously or with a similar dose of BGG simultaneously with 10 µg of endotoxin, were examined histologically at various days after injection. “Red” and “white” pulp of these spleens were cultured separately to study their ability to form antibody in vitro. It was found that an increased number of hemocytoblasts occurred in the white pulp starting 1 day after the antigen injection. Antibody formation in vitro was demonstrated at the time of immature plasma cell proliferation (day 4 to 7), and was much more pronounced in the “red” than in the “white” pulp. Histologically, most of the immature and mature plasma cells were found on the border of red and white pulp. Endotoxin enhanced the plasmacellular reaction, the serum antibody titers, and the formation of secondary nodules arising in the white pulp between days 5 and 13 after antigen. Since only slight production of antibodies was observed in the white pulp of some rabbits in the later phase of the response, the effect of endotoxin on the primary antibody response seemed mediated rather through its effect on plasma cell proliferation than through stimulation of secondary nodule formation. Most of the serum antibody formed by the rabbits in this study was destroyed by treatment with mercaptoethanol, indicating that the early primary response antibody belongs to the 19 S fraction of γ-globulin.