Monitoring of kidney and simultaneous pancreas-kidney transplantation rejection by release of donor-specific, soluble HLA class I.

Using an HLA-A2-specific ELISA we monitored daily pretransplantation and posttransplantation sera from five kidney and eight simultaneous pancreas-kidney HLA-A2-negative recipients of HLA-A2-positive transplants during hospitalization. We found that, unlike liver transplants, neither kidney nor simultaneous pancreas-kidney transplants continuously secreted donor HLA proteins. However, three of four rejection episodes in kidney recipients and seven of seven rejection episodes in simultaneous pancreas-kidney recipients were accompanied by elevated serum levels of donor sHLA-A2 (> 5 ng/ml). In only one kidney patient was there a release of donor antigen without evidence of rejection, but in the simultaneous pancreas-kidney group most patients had at least one time point of detectable sHLA-A2 without strong evidence of kidney rejection. While total sHLA levels were also elevated during rejection, the rise in donor-specific sHLA was more dramatic when compared to pretransplantation background levels. We hypothesized that the release of donor sHLA class I proteins by transplanted organs might be a systemic indication of rejection in both pancreas and kidney allografts. The detection of donor sHLA in recipient sera could be an important noninvasive monitor of rejection, especially in the pancreas, which is currently difficult to monitor as a single-organ transplant.