Induction of donor-specific T cell anergy by portal venous injection of allogeneic cells

The mechanisms behind tolerance induction by portal venous (pv) injection of allogeneic cells are investigated. When a hematopoietic stem cell (HSC)-enriched population of BALB/c bone marrow was pv injected into C57BL/6 mice, the response of the T cells in the B6 mice to BALB/c alloantigens in mixed lymphocyte reaction (MLR) decreased until day 4 after the injection. Neither clonal deletion of V(beta)11(+) T cell nor donor-specific suppressor activity was observed. When recipient T cells were separated into CD4(+) and CD8(+) cells, only the CD8(+) cell population showed donor-specific tolerance. The donor cells were trapped and retained in the host liver. MHC class I antigens were highly expressed on the trapped cells whereas class II antigens or B7 costimulatory molecules were not. The tolerance to BALB/c alloantigens in MLR was obtained also by the pv injection of Meth A, a BALB/c-derived sarcoma cell line. However, tolerance was not induced by the pv injection of B7-transfected Meth A cells. In addition to MLR, tolerance was also observed in DTH responses, and this was also due to the unresponsiveness of CD8(+) cells to the donor alloantigens, However, the BALB/c-specific DTH responses were not suppressed after the pv injection of B7-transfected Meth A cells. These results strongly suggest that the tolerance induced by pv injection of allogeneic cells is due to clonal anergy generated by the absence of costimulatory signals in the interaction between donor-specific CD8(+) T cells and donor hematopoietic cells trapped in the host liver.