Figure 816

Alternative approaches to human leukocyte antigen (HLA) matching. Because completely mismatched kidney transplantations function well over long periods, an alternative approach might begin with the hypothesis that six-antigen "mismatched" transplantations were not completely mismatched. Interest in reevaluating the potential roles of cross-reactive groups (CREGs) in transplantation is one such approach. In the early days of serologic HLA testing, a high panel reactive antibody sera was considered to be composed of many anti-HLA antibodies. It was later noted, however, that sera of highly sensitized patients awaiting solid organ transplantation were generally composed of a small number of antibodies directed at public antigens, also called CREGs, rather than multiple antibodies, each reacting with a specific conventional HLA antigen. Furthermore, the frequency of the CREGs was much higher, eg, 35% to 88%, than that of even the most common HLA-A and -B antigens. By inference, therefore, matching for donor and recipient antigens included in the same CREG, ie, CREG matching, could result in a higher number of matched transplantations and a lower level of sensitization in patients having repeat grafts. In addition, because of the inclusion of several private HLA-A and -B antigens within a single CREG, a number of relatively rare antigens can be matched more easily, offering the possibility of improved graft survival for a greater number of both white and nonwhite patients. (Adapted from Thelan and Rodey [4]; with permission.)

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