Immunological relevance of CREG matching in cadaver kidney transplantation

Background. On the basis of cross-reactive antibodies that react with different human leukocyte antigens (HLA) with shared epitopes, HLA-A and -B antigens can be assigned to cross-reactive groups (CREG). In the context of renal transplantation, it has been reported that matching for CREG results in improved graft outcome and reduces the requirement for rejection treatment. Because CREG matching also improves the equity of kidney distribution to ethnic minorities, a CREG-based cadaver kidney allocation policy was introduced in the United States a few years ago. Methods. The authors reexamined the immunologic relevance of matching according to CREG using the data of the international Collaborative Transplant Study. A total of 91,917 patients who received a first cadaver kidney transplant between 1991 and 2002 formed the basis of this analysis. Results. The authors found that the underlying impact of matching for HLA antigens accounts entirely for the observed positive effect of CREG matching. For patients with a particular HLA antigen match grade, matching for CREG had no advantageous effect on graft outcome or rejection treatment. An immunologic basis for CREG matching could thus not be found in this large analysis of cadaver kidney transplants. Conclusions. The findings indicate that CREG matching for kidney allocation is conceptually flawed from an immunologic viewpoint.