Immunosuppression by Friend leukemia virus is H-2 restricted by alloreactive T lymphocytes.

Friend leukemia virus suppresses mitogen-responsive cells in vitro by activating thymus-dependent suppressor cells. The interaction between T suppressor and mitogen-responsive cells is H-2D restricted by a third cell type, called an interfering cell. The interfering cells could be characterized as alloreactive T cells that functionally mature in the spleen at 2 weeks of age and that can be functionally inhibited by mitomycin C, irradiation, and cortisol. Interfering cells are stimulated by H-2D (and not H-2L) alloantigens of the mitogen-responsive cells. H-2D differences between interfering and T suppressor cells are unimportant. Induction of "tolerance" to H-2 alloantigens in semi-allogeneic radiation marrow chimeras resulted in the specific loss of interfering cell function. It is possible that interfering or similar cells participate in other forms of H-2 restriction.