Ly-49 G2(+) NK cells are responsible for mediating the rejection of H-2(b) bone marrow allografts in mice

NK cells can mediate the specific rejection of bone marrow but not solid tissue allografts in lethally irradiated mice. NK cells are also responsible for the phenomenon of 'hybrid resistance' in which F-1 hybrid H-2 heterozygous mice can reject parental H-2 homozygous bone marrow grafts, Ly-49C and Ly-49 G2 are markers identified on subsets of NK cells. While Ly-49C(+) NK cells have been demonstrated to mediate the specific rejection of H-2(d) bone marrow allografts, the role of the Ly-49 G2(+) NK subset is unclear because depletion of this subset in vivo did not affect splenic NK activity against tumor targets. Through bone marrow transplantation typing studies, we demonstrate that Ly-49 G2(+) NK cells complement Ly-49C(+) NK cells in that they specifically mediate the rejection of H-2(b) bone marrow allografts in lethally irradiated mice. In support of this, depletion of the Ly-49C(+) NK subset in vivo also enhanced the ability of the mice to reject H-2(b) bone marrow cells suggesting that the depletion was augmenting the ability of the Ly-49 G2(+) NK cells to reject the marrow allografts, Depletion of Ly-49 G2(+) NK cells in F-1 hybrid mice abrogated their ability to reject parental H-2(b) but not H-2(d) bone marrow grafts, Therefore, Ly-49 G2 denotes a subset of NK cells that appears to play a critical role in the recognition of H-2(b) bone marrow cells in allogeneic and F-1 hybrid mice.