Difference of rejection between heart and heart-lung transplantation in rats: flowcytometric analysis of graft infiltrating lymphocyte subsets.

Reported clinical and experimental observations indicate that heart grafts in combined heart-lung transplantation are less frequently rejected than heart grafts transplanted alone. In order to elucidate the mechanism of this difference, twenty-eight inbred male Lewis rats receiving heterotopic allografts from inbred male Fisher rats were evaluated for surface markers of graft infiltrating lymphocytes (GIL) and peripheral blood lymphocytes (PBL) using flowcytometry. Monoclonal antibodies investigated in this study were W3/25 (anti-helper T lymphocyte), OX8 (anti-suppressor/cytotoxic T lymphocyte), OX39 (anti-interleukin 2 receptor), and OX6 (anti-MHC class II antigen). In the acute study, a heart transplanted group (n = 7) and a heart-lung transplanted group (n = 7) without immunosuppression were studied. In the chronic study, cyclosporine (10 mg/kg/day i.m.) were administered in the heart transplanted group (n = 7) and the heart-lung transplanted group (n = 7). Both in the acute and chronic studies, the proportion of W3/25 positive cells in GIL of heart grafts of the heart transplanted group was significantly higher than that of heart grafts and lung grafts of the heart-lung transplanted group. OX8 positive cell proportion in GIL of heart grafts and lung grafts of the heart-lung transplanted group were significantly higher than that of heart grafts of the heart transplanted group. These results lead us to speculate that suppressor T lymphocytes are an important distinguishing factor in the rejection processes of heart allografts and heart-lung allografts as observed in clinical experience.