Prevention of rejection of allogeneic bone marrow transplants by NK 1.1 antiserum.

We have studied the effect of in vivo administration of NK 1.1 antiserum on two functions of natural killer (NK) cells: (A) in vitro cytotoxicity of B6 mice to T cell lymphoma, YAC-1, and (B) potential of B6 mice to reject allogeneic BALB/c bone marrow transplants. We demonstrated that a single i.v. injection of 0.4 ml of NK 1.1 antiserum significantly reduced in vitro NK cell cytotoxic potential and concomitantly prevented rejection of allogeneic bone marrow transplants. NK 1.1 antiserum was effective in diminishing both of these functions when injected 2, 6, or 24 hr before transplantation and NK cell assay, but it was ineffective when given 48 hr before transplantation or the NK cell test. As a specificity control, we investigated the effect of specific anti-T-cell-directed monoclonal antibodies, Thy 1.2 and Lyt 2.2, in the same systems. Neither of these antibodies exerted any effect on NK cell cytotoxicity to YAC-1 or rejection of allogeneic bone marrow transplants. These studies indicate that NK cells represent one of the major components of the mechanism of bone marrow graft rejection.