Splenic CD8+ (Lyt-2+) cells of C57BL/6 mice were injected into semiallogeneic (NZB x BXSB)F1 mice, which spontaneously develop lupus nephritis, in order to examine whether the disease was somehow modified by the occurrence of graft-versus-host reaction. The development of lupus nephritis in the F1 recipients was strongly inhibited and immunopathological parameters such as anti-DNA antibodies, circulating immune complexes (CIC) and splenic immunoglobulin-producing cells (IgPC) were markedly reduced. The injection of CD4+ (L3T4+) T cells into F1 recipients did not result in similar effects. These findings suggest that the development of autoimmune disease could be ameliorated by CD8+ cells responding to MHC class I antigens. The significance of the data is discussed in terms of the treatment of autoimmune diseases.