[Phenotypic and functional analyses of cells infiltrating rat hepatic allograft]

In order to elucidate the immunological characteristics of rat liver transplantation, graft infiltrating cells (GIC) were isolated from rat hepatic allografts, and phenotypic and functional analyses were performed. Long-surviving combination (Lewis engrafted BN liver, MST = 166.8 +/- 28.1 days, n = 10) and acutely-rejected combination (Lewis engrafted DA liver, MST = 9.6 +/- 0.3 days, n = 6) were compared. Relative proportions of all T cells and activated T cells assessed by flow cytometry were significantly higher in Lewis recipients of acutely-rejected combination than in those of long-surviving combination on day 6 after transplantation. Phenotypic analyses of GIC on days 6, 14, and 45 after transplantation in Lewis hosts of long-surviving combination were assessed. All T cells, OX-8 positive cells (Tc/s, NK), and OX-39 positive (IL-2 receptor) cells showed peak levels on day 6 and decreased on day 45. Cytotoxic activity of GIC toward donor lymphocytes on day 6 was stronger in host of acutely-rejected combination (18.9 +/- 4.0%, E/T = 50) than in that of long-surviving combination (5.3 +/- 2.8%). On the other hand, NK activity in Lewis host of long-surviving combination was high (17.5 +/- 3.0%, E/T = 100) on day 6 after transplantation. These results demonstrate that some immunosuppressive mechanism is present already on day 6 after transplantation, and that infiltration or activation of cytotoxic T cells is inhibited in long-surviving combination of rat hepatic allografts.