Ly-5 molecular forms in congenitally immunodeficient mice.

Four different molecular weight forms of the Ly-5 antigen were defined by immunochemical methods on the cell surface of murine spleen cells using a monoclonal antibody. Each form was selectively expressed by cells belonging to different lineages. A 220,000-dalton molecule was associated with B cells, a 200,000-dalton molecule with macrophages and two antigens of 185,000 and 175,000 daltons, respectively, were detected on the cell surface of normal thymocytes. The 185,000-dalton Ly-5 molecule was not found on the lymphoid cells of immunodeficient mice, like the athymic nude or the athymic-asplenic (LASAT) mice, suggesting that cells bearing this Ly-5 molecule have a significant function in some T-dependent immune responses.