FLOW CYTOMETRIC ANALYSIS REVEALS UNEXPECTED SHARED ANTIGENS BETWEEN HISTOLOGICALLY DEFINED POPULATIONS OF THYMIC STROMAL CELLS

Utilizing flow cytometry, the expression of antigens recognized by six thymic stromal cell (TSC) reactive mAbs was investigated on fresh TSC s and TSC lines. It was found that some thymic epithelial cells and de ndritic cells share antigenic phenotypes, and that most TSC reactive m Abs have a more extensive distribution than would have been predicted from immunohistology. While these findings illustrate the higher sensi tivity of flow cytometric analysis, they more importantly emphasize th e great complexity of TSC that direct T cell development. In order to identify the molecular parameters that define the various steps involv ed in T cell differentiation, TSC antigens (non-TCR/MHC/co-receptor) t hat are functional will have to be identified. This study represents t he initial steps in characterizing such antigens.