Major histocompatibility antigens in transplanted human hearts before perfusion.

The expression of major histocompatibility class I and II antigens is described in human normal donor hearts before perfusion with recipients' blood. Class I and II major histocompatibility antigens were found on interstitial but not on myocardial cells. Endothelial cells accounted for most of the generic class I reactions (that is, W6/32 and beta 2 microglobulin), and endothelial cells accounted for most of the HLA-DR and -DP reactivity. HLA-DQ antigens were not found in this series of normal donor hearts. The earliest time we were able to identify HLA-DQ antigens during the follow-up biopsies from these patients was 1 week after the allograft had been in place. Macrophages accounted for little of the class II reactivity. Variations in the HLA-DQ antigen expression on endothelial cells may be useful in the follow-up of transplanted hearts, considering that these antigens have been found to be more susceptible to the effects of interferon-gamma than either HLA-DR or -DP.