Different expressions of Ly-49 receptors on mouse NK and NK T cells.

: NK T cells are a unique T cell lineage and are reported to express Ly-49 molecules which are inhibitory receptors specific for class I molecules. In this study, we examined the expression of activation and inhibitory receptors on NK T cells in different organs of beta2-microgloblin knock out (beta2mKO), C57BL/6 (B6; H-2b), C57BL/10 (B10; H-2b) and B10.D2 (H-2d) mice. The low level expression of inhibitory receptors Ly-49A and G2 on NKT cells as well as NK cells, which are specific for Dd antigen, were observed in B10.D2 mice, but not in beta2mKO, B6, or B10 mice. The small percentage of inhibitory receptor Ly-49C positive NK and NKT cells, which is specific for Kb and Dd antigens, was observed in BMC, LMC and SC of B6, B10 and B10.D2 mice compared to beta2mKO mice. On the contrary, the large percentage of Ly-49C positive NK T cells was observed in thymocytes of B6, B10 and B10.D2 mice compared to beta2mKO mice. Interestingly, Ly-49D activation receptor was hardly detectable on NK T cells in any organs of the 4 strains of mice whereas it was clearly detectable on NK cells. These findings suggest that the unique characteristics of NK T cells may mediate regulatory function in MHC class I antigen-restricted immunity.