REGULATION OF EARLY COMPLEMENT COMPONENTS C3 AND C4 IN THE SYNOVIUM

To determine the cytokine inducibility of early complement component ( C3 and C4) expression in the synovium, explant tissue was maintained i n culture for 7 days. C3 and C4 production was measured by specific en zyme-linked immunosorbent assay, and RNA was evaluated by semiquantita tive PCR, The effects of leukemia inhibitory factor (LIF), gamma inter feron (IFN-gamma), IFN-alpha, and estrogen on C3 and C4 expression wer e evaluated. C3 levels were unaffected by 7 days of LIF, IFN-gamma, or IFN-alpha treatment. In contrast, C4 levels were significantly induce d in synovial samples treated for 7 days with either IFN-gamma or IFN- alpha. LIF had no effect on C4 levels in this system. Estrogen was fou nd to down-modulate the induction of expression due to IFN-gamma. Thes e data provide evidence for cytokine regulation of C4 expression in th e synovium and for estrogen modulation of those effects.