EFFECT OF GAMMA-INTERFERON ON THE SYNTHESIS OF THE FUNCTIONAL ALTERNATIVE AND TERMINAL COMPLEMENT PATHWAYS BY HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS IN-VITRO

The cytokine gamma-interferon (gIFN) has been reported to modulate synthesis by endothelial cells (EC) of alternative pathway complement factors (H, I, and B). However, the net effect of gIFN on the synthesis and expression of the functional alternative and terminal pathways has not yet been reported. EC cultured under serum-free conditions were treated with different concentrations of gIFN and simultaneously co-incubated with agarose beads, which activate the alternative pathway. C3b and the terminal complement complex (TCC) bound to co-incubated beads were measured by radioimmunoassay using anti-human C3c and TCC antibodies. gIFN in concentrations 500-4000 U/ml increasingly reduced the amount of C3b and Tcc detected on the beads. The down-regulating effect of gIFN on EC complement biosynthesis may be physiologically relevant by locally controlling complement activation.