Ly-6C is a member of the Ly-6 multigene family of type V glycophosphatidylinositol-anchored cell surface proteins. It is expressed on bone marrow cells, monocytes/macrophages, neutrophils, endothelial cells, and T-cell subsets. Mice with the Ly-6.2 allotype (e.g., AKR, C57BL, C57BR, C57L, DBA/2, PL, SJL, SWR, 129) have subsets of CD4+Ly-6C+ and CD8+Ly-6C+ cells while Ly-6.1 strains (e.g., A, BALB/c, CBA, C3H/He, DBA/1, NZB) have only CD8+Ly-6C+ lymphocytes. Ly-6C may play a role in the development and maturation of lymphocytes.