||Cytotech, Inst., San Diego, CA. ;Mellon Inst.-Union Carbide Corp., Export, PA. Bushy Run Research Center. ;Union Carbide Corp., Danbury, CT.;Environmental Protection Agency, Washington, DC. Office of Toxic Substances.
The ability of MIC to induce complement activation in vitro and in vivo was investigated. For the in vitro studies, both human and guinea pig serum or EDTA-plasma sample were exposed to 1167-1260 ppm MIC vapor for 15 min at room temperature. The human serum samples exposed to MIC showed significant reductions in Factor B, C2, C4, C3, C5, and total hemolytic complement CH50 activity levels. C6 functional activity was unaffected. The C3, C5 and CH50 functional activities in guinea pig serum (the only functional tests conducted on these samples) were more sensitive to MIC mediated reduction than the corresponding activity reductions observed in the human serum samples. The human and guinea pig EDTA-plasma samples exposed to MIC vapor showed no evidence of C3 consumption but did show significant reductions in CB50 levels. Thus, MIC vapor was able to activate, and thereby reduce serum complement C3 activity in vitro by a complement-dependent process. However, at least one complement component other than C3 was inactivated in EDTA-plasma by a complement-independent mechanism.