Human Thymic Epithelial Cells in Serum‐Free Culture: Nature andEffects on Thymocyte Cell Lines

Thymic epithelial cells (TEC) have been cultured for several months and/or for 4 to 5 transfers in a growth factor-defined serum-free medium without concurrent growth of other cell types. The use of monoclonal antibodies and alpha MAM-6 indicated that the majority of TEC were of medullary origin. The vast majority of cells were positive for LFA-3 and class I, and class II expression was low or absent. Supernatants from the cultures were shown to contain IL-1 beta, IL-6, and M-CSF. Coculture of cloned subpopulations of thymocytes and TEC showed effects of TEC and of secreted ILs on thymocyte proliferation. High percentages of TEC were able to bind DN, DP, or SP thymocyte populations, partly via CD2-LFA-3 adhesion. Thus, it is possible to culture TEC without unknown serum factors and with maintenance of functional activities.