Weak humoral posttransplant alloresponse after a well-HLA-matched cadaveric kidney transplantation

Background: Screening of donor-specific antibodies or alloantibodies after kidney transplantation has not been performed routinely. The aim of this study was to evaluate the Immoral antidonor and alloresponse of immunologically low-risk recipients of cadaveric renal allografts during the first posttransplant year. Methods: Alloresponse against the donor was analyzed by means of T-cell immunoglobulin (Ig)G and IgM and B cell IgG flow cytometric crossmatch (FCXM) tests with sera from days 0, 21, 90, and 365 posttransplant. In addition, panel reactive anti-human leukocyte antigen (HLA) class I and class II antibodies (PRA I and PRA 11) were analyzed using flow cytometric methods. The recipients were treated either with a low initial cyclosporine regimen with single-bolus antithymocyte globulin (ATG) or basiliximab induction or conventional cyclosporine triple therapy. Results: No significant posttransplant anti-HLA class I or class II sensitization was found in the recipients as a whole. Recipients receiving a single-bolus ATG showed significantly higher proportion of PRA I positivity in the day 21 sample compared with the other groups. Flow cytometric donor-specific T- and B-cell IgG alloresponses remained low, but the proportion of T-cell IgM crossmatch-positive recipients increased during the study. Positive T-cell IgM FCXM was found to be associated with acute rejection episodes and cytomegalovirus (CMV) infections. Conclusions: In immunologically low-risk kidney-graft recipients, positive T-cell IgM FCXM at transplantation was found to be a risk factor for rejection episodes. Conversion of T-cell IgM FCXM to positive was found to be associated with CMV infections.