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Although there is an increasing body of evidence for a deleterious effect of mismatched donor HLA antigens on the outcome of human cardiac transplantation, the role of anti-HLA lymphocytotoxic antibodies remains controversial. Thus, their appearance after cardiac transplantation has been associated with poor outcome by some groups; whereas others have reported them to be of no clinical significance. Furthermore, their presence prior to cardiac transplantation has also been the subject of similarly conflicting reports. The deleterious effect of such pre-existing antibodies has been predicted by a positive lymphocyte cross-match (LCM), which, for most patients awaiting renal transplantation and in many requiring a cardiac allograft, leads to cancellation of the operation. The reason for undertaking the current study was to test the hypothesis that the constraints which a positive LCM result impose in preventing renal transplantation may not apply to orthotopic heart transplantation (OHT).Four sensitized patients underwent OHT across a positive prospective LCM. Three were females, and one of those females also underwent cadaveric renal transplantation at the time of OHT. All four patients received aggressive early post-transplant immunosuppressive therapy, which included plasmapheresis, intravenous immunoglobulin (IVIg), antiproliferative agents (cyclophosphamide, basiliximab) and cytokine down-regulators (calcineurin inhibitors, muromonab-CD3) and anticell antibodies (OKT3, ATG). They also received standard immunosuppressive therapy which included corticosteroids. Complement-dependent cytotoxicity (CDC) was used for the identification of anti-HLA lymphocytotoxic antibodies. Reactivity of the latter against more than 10% of a panel of well-characterized T cells was considered sensitization, and required LCM to be performed prospectively, which test was also performed using the CDC technique.Three of the patients exhibited evidence suggestive of acute or hyperacute rejection in endomyocardial biopsy specimens by postoperative day (POD) 7. Two of the three patients with rejection also exhibited haemodynamic instability (elevated filling pressures and reduced cardiac index) on POD 1, which improved with inotropic support. One patient sustained a cardiac arrest on POD 7, and was successfully resuscitated without sequelae. All patients are now doing well, postoperatively (follow-up: 17–57 months) post-transplant. Two patients have normal left ventricular function and one patient has mild left ventricular dysfunction. Two have no further evidence of sensitization (PRA < 10%).Although the number of patients in this study is small, the long-term successful outcome of OHT following positive prospective cross-matches suggests that such a test result, in contrast to the restraints it imposes on renal transplantation, may not be a contra-indication to transplantation of the human heart. If OHT proceeds after the LCM is reported positive, aggressive immunotherapy should not only be initiated early, but should also be targeted at humoral-vascular rejection in particular.