Incidence of humoral rejection in heart transplant recipients treated with tacrolimus or cyclosporine A.

HUMORAL rejection is a rare but potentially fatal form of acute allograft rejection. Pathophysiologically, allosensitization against graft determinants occurs either preor posttransplantation. Preformed antibodies lead to the phenomenon of hyperacute rejection. The de novo synthesized antibodies directed against HLA antigens expressed on graft endothelium are clearly associated with humoral rejection. The diagnosis is made by histologic criteria of endothelial swelling and vasculitis and by immunohistologic demonstration of deposition of complement split products. This study was designed to explore the incidence of humoral rejection in human heart transplant recipients treated either with cyclosporine A (CyA) or tacrolimus (FK506). As a marker for humoral rejection, C4d complement fragment was used, originally described in kidney allografts, which we introduced as a marker for the diagnosis of acute humoral rejection in heart transplantation.