Rejection of a kidney transplant does not always lead to priming of cytotoxic T cells against mismatched donor HLA class I antigens

Background, Previous studies showed that graft rejection is often associate d with the presence of primed cytotoxic T cells (CTLs) with a high avidity for donor cells. Similar high avidity CTLs have been found in individuals w ho have formed IgG anti-HLA antibodies, The presence of such CTLs to a spec ific HLA mismatch is therefore considered to be a reflection of an activate d immune system, and a contraindication for retransplantation with a donor sharing this particular HLA class I mismatch. Methods. In our study we investigated whether patients have always primed C TLs against all individual HLA class I mismatches present on a rejected gra ft. Therefore, 14 patients who had undergone transplantectomy after irrever sible kidney graft rejection were analyzed with respect to donor-specific C TLp frequencies and the presence or absence of high avidity CTLs directed a gainst HLA class I mismatches present on the rejected graft. Results. Patients, who have not formed anti-HLA antibodies against the dono r have mainly naive CTLs, Most of the patients, that have developed IgG ant i-HLA antibodies against a donor mismatch, have primed CTLs directed agains t that particular mismatch, However, patients with IgM anti-HLA antibodies only, and patients with IBG anti-HLA antibodies in historical sera but no I gG anti-HLA antibodies in current sera, have mainly naive CTLs against the donor HLA mismatch. Conclusion. Our results suggest that it is not always necessary to exclude repeated HLA class I mismatches for a subsequent transplantation. In additi on to good anti-HLA antibody screening, the CTLp-assay may be a useful tool for donor-selection in retransplant candidates.