The effect of cyclosporine treatment on the expression of genes encoding granzyme A and perforin in the infiltrate of mouse heart transplants.

Following activation of cytotoxic T cells and NK cells several genes encoding proteins putatively involved in cell-mediated cytotoxicity become expressed. The expression of genes encoding the cytotoxic T cell associated serine protease granzyme A and perforin was analyzed in cellular infiltrates of MHC mismatched (H-2d-->H-2k) heterotopic heart transplants both in immunosuppressed recipients treated with cyclosporine and in untreated recipients. Heart transplants were completely rejected by untreated animals on day 10 post-transplantation, whereas CsA treatment generally prolonged survival of the transplants beyond 30 days. In untreated recipients the number of granzyme A- and perforin-expressing cells in heart transplants increased from approximately 10 granzyme A-positive cells/mm2 and 1 perforin-positive cell/mm2 on day 2 posttransplantation to over 80 positive cells for both genes on day 5 posttransplantation. In contrast, these values remained always below 15 positive cells/mm2 for both genes between day 5 and day 30 posttransplantation in CsA-treated recipients. Comparison of the frequency of CD8+ T cells in the infiltrates showed that lower numbers of perforin and granzyme A-positive cells were mainly due to the immunosuppressive action of CsA rather than to reduced infiltration of transplants. The present study shows that expression of granzyme A and perforin gene can be used to discriminate between quiescent and activated cytotoxic cells also in immunosuppressed animals and further confirms that these can be used as sensitive markers for monitoring the fate of a transplant.