Soluble MHC class I antigens (sHLA) and anti-HLA antibodies in heart and kidney allograft recipients.

Soluble HLA (sHLA) antigens were measured in a panel of 50 renal and 50 cardiac graft recipients by a quantitative ELISA over periods ranging between 2 months and 3 years. 72% of the renal patients and 68% of the cardiac graft patients experienced episodes of acute rejection during the observation period. sHLA were elevated to over 2-5 times the normal levels up to 10 days before histological evidence of rejection. This duration was for each individual patient very variable. Cytomegalovirus (CMV) infections did not appear to elevate sHLA levels. Donor-specific HLA-A2 was measured in only 1 cardiac recipient. 15% of the sera obtained from cardiac patients had cytotoxic anti-HLA antibodies, when tested against a panel of 50 test cells. After thermal inactivation at 56 degrees C, 42.5% of the sera became positive against at least 10% of the test cells. This finding suggests thermal dissociation of immune complexed anti-HLA antibodies. sHLA measurement and careful monitoring of serum for the presence of cytotoxic anti-HLA antibodies in graft patients are useful techniques which could help predict the long-term fate of an allograft.