Serial ten-year follow-up of HLA and MICA antibody production prior to kidney graft failure

The role of HLA antibodies in chronic allograft rejection was examined utilizing a unique resource of sera collected annually and stored over a 12-year period from patients with rejected or retained grafts. In patients selected for not having preformed HLA antibodies, 679 postoperative serial serum samples from 39 patients who rejected their grafts and 26 with functioning grafts were tested for HLA Class I and Class II antibodies by flow cytometry and for MICA antibodies by cytotoxicity on recombinant cell lines. HLA antibodies were found in 72% of patients who rejected grafts, compared to 46% with functioning transplants (p < 0.05). In addition, the incidence of IgG HLA plus MICA antibodies was higher (77%) among those with failed transplants than those with functioning transplants (42%) (p < 0.01). Finally, if patients with IgM anti-HLA antibodies were included, 95% of the 39 patients who rejected their grafts had HLA or MICA antibodies, compared to 58% with functioning grafts (p < 0.01). Patients who rejected transplants had HLA and MICA antibodies more frequently than those with functioning grafts. These antibodies found in the peripheral circulation, were not necessarily donor-specific, but their association with failure is consistent with a causality hypothesis.