CD46 and hemolytic-uremic syndrome: Study of families with a history of HUS has implicated mutations in several proteins responsible for regulating the alternative complement pathway, namely complement factor H,65 membrane cofactor protein (MCP), and factor I (IF),66 as well as thrombomodulin.67 Exposure to agents potentially toxic to the vascular endothelium (such as certain viruses, bacteria, toxins, immunocomplexes, and cytotoxic drugs) may initiate local intravascular thrombosis.68 This action promotes C3bBb convertase formation and complement deposition within capillary vessels.