Effects of macrophage culture supernatants (monokines) on phagocytosis, catabolism, lysosomal enzymes and cyclic amp of isologous macrophages

Monokines (48 h-culture supernatants) obtained from resting mouse peritoneal macrophages were found to modify various fundamental functions of newly prepared isologous target macrophages. Thus, the cellular level of cyclic AMP showed a rapid though transient increase, whereas the release of a lysosomal marker enzyme (β-glucuronidase), phagocytosis and catabolism of endocytosed particles were all inhibited. Inhibition was dose-dependent but the various functional parameters studied showed important individual differences in responsiveness: release of β-glucuronidase > phagocytosis of zymosan and sheep erythrocytes > catabolism of endocytosed sheep erythrocytes. Neither the release of monokines nor the expression of their effects required the presence of serum in culture medium or that of lymphocytes in macrophage suspensions and in no case could these effects be attributed to cytotoxicity or to the presence of breakdown products from lyzed cells.