Biochemical studies on stimulation of mouse peritoneal macrophages by interaction with preformed immune complexes. 
Mouse peritoneal macrophages (MPM) were observed to be stimulated by both in vivo and in vitro interactions with preformed HSA-anti HSA immune complexes (IC) having different antigen-antibody ratios.  This was indicated by cellular alterations in morphology, increase in cellular protein and lysosomal enzyme contents and a marked fall in 5' nucleotidase level.  Analysis of cellular proteins of IC-elicited cells by SDS-polyacrylamide gel electrophoresis showed accumulation of 80, 47, 33, 28, 18 and 14 kDa proteins.  Insoluble immune complexes at equivalence (IC-Eq) was found to be more effective in the stimulation process as compared to the soluble antigen excess complexes (IC-Ag).  These IC-elicited cells secreted lesser amounts of lysosomal hydrolases when explanted in culture medium as compared to resting cells, whereas in vitro stimulation of resident MPM with IC resulted in enhanced lysosomal hydrolase release.  IC-induced lysosomal secretion was time and dose dependent and varied with the nature of the complexes.  Complement coated immune complexes (IC-CC) induced maximum enzyme secretion followed by IC-Eq and IC-Ag.