MHC antigen expression in sequential biopsies from cardiac transplant patients--correlation with rejection.

Class I induction on the myocardium of transplanted heart was investigated with regard to its temporal relationship to rejection episodes, how it is affected by anti-rejection therapy and whether it is dependent upon the presence of a T cell infiltrate in the biopsy. Sequential cardiac biopsies (total 114) from 11 patients from the time of transplant to 1 year after transplant were studied using immunocytochemical techniques. The effect of different immunosuppressive regimens on MHC antigen expression was also studied. All the biopsies diagnosed as showing rejection for the first time showed induction of Class 1 on the myocardium with 79% during subsequent rejection episodes. Class I induction was associated with a leucocyte infiltrate, not always containing T cells, and disappeared in 47% of biopsies taken 3-4 weeks after treatment with steroids and/or ATG. Increased expression of Class II, in particular DQ antigens on interstitial structures, paralleled Class 1 induction. MHC antigen expression returned to normal in 8/9 patients, at 1 year after transplant. Different immunosuppressive regimens affected the number of biopsies showing Class 1 induction on the myocardium. Our results suggest that in clinical heart transplantation class I induction is related to the rejection process.