C4d (SP91)

C4d is a stable split product remnant of classical complement activation which becomes covalently bound to endothelium and basement membrane after induction of the classical antibody-induced pathway. As an established marker of antibody-mediated acute renal allograft rejection (AR) and its proclivity for endothelium, this component can be detected in peritubular capillaries in chronic renal allograft rejection as well as hyperacute rejection, acute vascular rejection, acute cellular rejection, and borderline rejection. It has been shown to be closely correlated with transplant kidney graft survival1-3. Anti-C4d, combined with anti-C3d, can be utilized as a tool for diagnosis of AR that may serve to warrant prompt and aggressive anti-rejection treatment1-6.