In Vitro Modulation of C1q MRNA Expression and Secretion by Interleukin-1, Interleukin-6, and Interferon-gamma in Resident and Stimulated Murine Peritoneal Macrophages

The complement system plays an important role in the humoral immune response. Activation of the classical complement pathway is mediated by its subcomponent, C1q. Among the main C1q-synthesising tissues, macrophages have been attributed as a source of particular importance. We investigated the effects of cytokines (IL-1, IL-6 and Interferon-gamma) on local C1q mRNA expression and C1q secretion in resident and in thioglycollate-stimulated murine peritoneal macrophages in vitro. The macrophages were isolated from murine peritoneal lavage fluid, maintained in culture and incubated with the cytokines. Among the cytokines, only IL-6 had a stimulatory effect on C1q production (25% increase vs. control), while IL-1 and interferon-gamma had an inhibitory effect (50% decrease vs. control), especially in stimulated peritoneal macrophages in culture. Our data suggest that C1q production in macrophages may be differentially regulated by inflammatory cytokines such as IL-1, IL-6 and interferon-gamma, the response being dependent on macrophage activation.