Differences in antigen handling by peritoneal macrophages from the Biozzi high and low responder lines of mice

Abstract

Abstract Peritoneal macrophages were isolated from high (Ab/H) and low (Ab/L) responder mice and their in vitro handling of three isotopically labeled antigens, 125 I‐labeled keyhole limpet hemocyanin ( 125 I‐KLH), 14 C‐labeled type 3 pneumococcal polysaccharide complexed with methylated bovine serum albumin ( 14 C‐SIII‐MBSA) and ( 14 C‐LE), studied in relation to the immune responses which these compounds evoke in the corresponding animals. There was a striking morphological difference between cultured Ab/H and Ab/L macrophages and the latter showed higher lysosomal enzyme activities. All three antigens were taken up faster by Ab/L macrophages. The intracellular digestion of 125 I‐KLH was also more rapid in these cells. Membrane‐bound 125 I‐KLH was persistent in Ab/H macrophages, but disappeared rapidly from the Ab/L cells. After the uptake of 14 C‐SIII‐MBSA complexes, more was retained by Ab/L macrophages, although probably localized in the interior of the cell, not on the membrane. Following the exposure of the cells to 14 C‐LE, there seemed to be an equivalent degree of continuing association of the polysaccharide with Ab/H as well as Ab/L cells. Thus, KLH and SIII, which evoke maximal and minimal antibody production in the two mouse strains, were handled differently by Ab/H and Ab/L macrophages. On the other hand LE, which elicits equivalent IgM synthesis in both mouse strains, had a similar fate in the two kinds of macrophages. The results suggest that macrophages express genes which control the humoral immune responses in the high and low responder animals and that antigen presentation on the macrophage membrane is a major factor regulating antibody production in these mice.