FT-2 antigen for distinguishing lymphocyte subpopulations in the developing thymus

Abstract The surface phenotypes of lymphoid cells in the developing embryonic thymus were characterized by using monoclonal antibodies. FT-2 antigen thus defined was predominantly expressed on thymocytes in the earlier embryonic stages in all the inbred mouse strains tested. The immunofluorescence and immunoperoxidase tests indicated that, like FT-1 antigen, the proportion of FT-2 + fetal thymocytes rapidly decreased with increase in gestation time, and these cells disappeared by day 19 of gestation. The treatment of fetal thymocytes with anti-FT-1 plus complement eliminated not only FT-1 + , but also FT-2 + cells, whereas the treatment with anti-FT-2 failed to eliminate approximately 40% of FT-1 + cells, suggesting that embryonic thymocytes can be provisionally divided into at least three subpopulations, FT-1 + 2 + , FT-1 + 2 − and FT-1 − 2 − .