Thymic epithelial cell-derived supernatants sustain the maturation of human prothymocytes: involvement of interleukin 1 and CD23.

During their development, human CD7+ lymphoid stem cells migrate into the thymus where, following intimate contact with thymic tissue, they proliferate and differentiate into functionally mature T lymphocytes. In this study, we investigated the effect of thymic epithelial cell-derived supernatants (TEC-SN) on early CD7+CD2-CD3- thymocytes. Our results indicate that TEC-SN are able to promote CD2 and CD3/TcR alpha/beta expression by CD7+ precursors. This activity correlated with soluble CD23 and interleukin 1 levels in TEC-SN. Furthermore, monoclonal antibodies to these cytokines decreased in vitro maturation of prothymocytes. Thus, in addition to cell-cell interactions, human TEC produce cytokines able to support early steps of thymocyte differentiation.