Faculty Bibliography

Langerhans cells are Ia-bearing antigen-presenting cells in the epidermis that share many functions with macrophages. We have used monoclonal antibodies to the macrophage antigens, Mac-2 and-3, Ia antigen, Fc fragment receptor and the common leukocyte antigen CLA to compare the cell surface antigens of these cells with those of interdigitating and follicular dendritic cells and of macrophages in lymphoid tissues. Immunoperoxidase staining was carried out with epidermal sheets from BALB/c mice and epidermal cell suspensions enriched for Langerhans cells by Fc rosetting. Langerhans cells stained for all of these antigens. Comparison with the staining properties of other dendritic cells and macrophages, in combination with previous observations, indicates a close relationship of Langerhans cells to the interdigitating cells of lymphoid tissues.

The ontogeny of the ability of thymus cells to "help" the response to a T-dependent antigen was studied in a cell transfer system. Lethally irradiated, thymectomized mice were reconstituted with thymus cells from donors of various ages together with rabbit anti-mouse brain antiserum and complement- (C) treated bone marrow cells. Mice were immunized with TNP-BGG and the magnitude and affinity distributions of their splenic plaque-forming cell (PFC) responses were assayed 3 weeks later. The results indicate that neonatal thymic cells are capable of helping a direct PFC response but cannot mediate the shift to indirect plaque formation. The ability to mediate the switch to an indirect PFC response is a separate maturation event that occurs between birth and 2 to 4 days of age. The thymus cell population from 2-day-old donors is already capable of mediating selection of high affinity PFC. Neonatal cells residing in an irradiated, thymectomized or nonthymectomized adult recipient for 7 days, even in the presence of adult rabbit anti-mouse brain and C-treated syngeneic spleen cells, did not mature to be capable of mediating an indirect PFC response.