Identifying subpopulations of thymic epithelial cells by flow cytometry using a new specific thymic epithelial marker, Ly110

We generated monoclonal antibodies reacting to a mouse thymic epithelial cell specific membrane protein, Thymic Stromal Co-transporter (TSCOT)/Ly110. These antibodies showed specificity to the peptide sequences derived from TSCOT/Ly110 determined by specific peptide inhibition in flow cytometric analyses with cells expressing the protein on the surface. TSCOT/Ly110 expressing subpopulation can be identified among the CDR1+ or 6C3+ cortical epithelial cells. Furthermore, CDR1 positive cortical thymic epithelial cells can be separated into further distinguishable populations; CDR1+6C3+Ly110+, CDR1+6C3−/lowLy110+, CDR1+Ly110−. Some of TSCOT/Ly110 expressing cells negative for both CDR1 and 6C3 markers were found at the earlier stages of development, while most of the cells are positive for both at 1-week-old stage. After then, downregulation in 6C3 and/or CDR1 expression was noticed until 16 weeks of age. These results suggest that TSCOT/Ly110 is a new marker for the subpopulation of CDR1+ or 6C3+ epithelial cells in the neonatal and adult thymus and is useful for the studies on the epithelial cell differentiation process.