Ly-6A/E Products

Ly-6A/E, also known as Sca-1, is a member of the Ly-6 multigene family of type V glycophosphatidylinositol-anchored cell surface proteins. (1-3) It is expressed on multipotent hematopoietic stem cells in bone marrow of mice with both the Ly-6.1 and Ly-6.2 allotypes. (4-6) In the periphery, Ly-6A/E exhibits a pattern of expression which is based on differences between the two allotypes. Ly-6.1 strains (e.g., A, BALB/c, CBA, C3H/He, DBA/1, NZB) have few Ly-6A/E+ resting peripheral lymphocytes, whereas Ly-6.2 strains (e.g., AKR, C57BL, C57BR, C57L, DBA/2, PL, SJL, SWR, 129) have relatively high numbers of Ly-6A/E+ lymphocytes. (1, 7-9) The expression of Ly-6A/E is dramatically upregulated in all strains upon cellular activation. (1, 8, 9) Studies with MAb D7 suggest that Ly-6A/E may be involved in B and T lymphocyte responses, (9-12) and it appears that the antigen may be required for T-cell receptor-mediated T-cell activation. (3, 13)