The relationship of anti-MICA antibodies and MICA expression with heart allograft rejection.

The role of MICA antibodies in acute heart allograft rejection was examined utilizing 190 pre- and post-transplant serum samples from 44 patients collected during the first year after transplantation. MICA antibodies were detected by CDC test on recombinant cell lines and by the newly developed Luminex MICA antibody detection assay. Additionally, MICA expression was analyzed by 'real time' RT-PCR and by immunohistochemistry in 10 endomyocardial biopsies. Only two subjects had HLA antibodies post-transplant. Nevertheless, MICA antibodies were found in a significant number of subjects. The prevalence of MICA antibodies was significantly higher among those with severe acute rejection (AR) than in those without rejection (60.7% vs. 14.3%, p = 0.0038 by CDC; 55.5% vs. 5.7%, p = 0.0020 by Luminex). In most cases, the appearance of MICA antibodies post-transplant precedes AR. Following transplantation, MICA up-regulation correlated with histological evidence of severe rejection. Monitoring for MICA antibodies post-transplant may be useful to establish new risk factors for acute rejection.