Hybrid and allogeneic resistance to T cell grafts mediated by murine NK and CD8+ T cells.

Lethally irradiated mice can reject H-2 allogeneic or parental strain stem cells in bone marrow cell (BMC) grafts within 48 h after transplantation. This rapid rejection of BMC grafts occurs without prior sensitization and is mediated by NK1.1+ NK cells. One hypothesis to account for the ability of host NK cells to mediate acute rejection of allogenic and parental stem cells is that these effector cells recognize hemopoietic histocompatibility (Hh-1) Ags on the donor stem cells. T cells present in the donor BMC can prevent NK cell-mediated rejection. However, lethally irradiated mice can also reject T cells present in lymph node cell preparations that respond to alloantigens of the host. T cell grafts from H-2k/Hh-1k, H-2r/Hh-1null, and H-2ia1/Hh-1null donors were rejected by CD8+ NK1.1- T cells. Ags other than Hh-1 Ags appeared to be recognized by these CD8+ T cells. In contrast, host NK cells rejected H-2d/Hh-1d T cell grafts, whereas both NK cells and CD8+ TCR-alpha beta + T cells rejected H-2b/Hh-1b T cell grafts. Therefore, both CD8+ TCR-alpha beta T cells and NK cells mediate allogeneic and hybrid resistance to T cell grafts.