Studies on the possible involvement of complement component C3 in the initiation of acid hydrolase secretion by macrophages. I. Correlation between enzyme-releasing and complement-activating capacities of several secretagogues.

A possible relationship between activation of the alternative pathway of complement and acid hydrolase secretion by macrophages has been investigated in vitro by examining the dose--response characteristics of several immunological and non-immunological stimuli of these two processes. Zymosan particles, insoluble immune complexes, methylamine and several other primary aliphatic monoamines were all found to elicit the selective release of lysosomal enzymes from macrophages by a process that correlated well with the ability of these agents to bring about consumption of haemolytically-active components of the alternative complement pathway. By contrast, substances which failed to activate the alternative complement pathway, i.e. soluble aggregated immunoglobulin and several primary aliphatic diamines, were found to be likewise incapable of inducing the selective release of lysosomal glycosidases from macrophages. These observations are interpreted as further evidence for imputing a role for complement C3 in the initiation of lysosomal enzyme release from macrophages.