RESUMO
Significantly lower graft survival has been observed among recipients of a third (G3) compared with a first or second kidney transplantation. Because patients awaiting G3 are largely HLA immunized, they are usually transplanted with a high HLA match. Moreover, their rate of acute rejection episodes is similar to a first or second transplantation. Since major histocompatibility complex class I related chain A (MICA) molecules have been proposed as new targets for antibody recognition, we were interested to type donors and recipients for MICA alleles and to study MICA immunization of these patients. Forty-three pairs of donors and recipients were typed for MICA alleles using Luminex technology (LABtype RSSO). MICA alleles showed strong linkage disequilibrium with the B locus: some 4-digit alleles were preferentially associated with a given MICA allele. A greater frequency of patients with 2 MICA mismatches (MM) was observed among patients with rejection (40%), whereas all the graft losses were observed in patients with 0 or 1 MICA MM. MICA immunization was studied using sera from 52 patients collected on day 0 and after transplantation using a Luminex assay (LABScreen). MICA immunization was less frequent than HLA immunization, and MICA donor-specific antibody (DSA) was equally present in functional and failed grafts. These observations confirmed the potential role of MICA immunization in rejection, whereas the poor graft survival among third transplantations could not be explained by MICA incompatibility or immunization.
