The value of flow cytometric crossmatch in cardiac transplantation

Abstract

One of the major clinical problems in cardiac transplantation is that of moderate rejection of the graft, and over the past few years there is increasing evidence that humoral antibody may be important in graft prognosis. The sensitivity of the conventional cytotoxic crossmatch has been questioned, and an increased significance of there of the flow cytometric crossmatch (FCXM) to detect the presence of antibodies before transplantation has been reported. In this study we have examined the sera of 138 cardiac transplants (1988-1992) for the presence of donor-directed IgG and IgM antibodies using FCXM. Sera were collected immediately before transplantation and before the institution of immunosuppressive therapy. All pretransplant cytotoxic crossmatches were negative. After a minimum follow-up period of 3 months, the performance of the transplants was graded by endomyocardial biopsy: 1, no or mild evidence of rejection; 2, patients showing moderate rejection requiring increased immunosuppression. Of the 138 patients studied, 10 patients were excluded as they died within the first week of transplantation. Eight children were excluded since they were given prophylactic ATG (Merieux). A positive FCXM result was defined as showing values in excess of that found for the AB control sera. A significant association was found between the presence of both IgG to T and B cells and IgM to T cells and graft performance (P = 0.02 and 0.93, respectively). Indeed, IgM-directed T-cell antibodies were only found in patients with moderate rejecton. These two groups were mutually exclusive, so that the FCXM was able to identify the presence of moderate rejection in 55% of the patients. In conclusion, results show that pretransplant FCXM in cardiac transplantation provides a more sensitive assay of antibody status in recipients and has proved to be of prognostic value.