Identification of TL+ thymocytes with different Lyt phenotypes.

The surface antigenic phenotype of BALB/c thymocytes has been analyzed by sequential cytotoxic treatment with Lyt-1.2, Lyt-2.2 and TL.2 antisera plus complement. Two new minor subpopulations with TL+Lyt-1+2- and TL+Lyt-1-2+ phenotypes have been identified providing direct evidence for the heterogeneity of the Lyt phenotype among the TL-positive supopulation of thymocytes. This finding suggests that differentiation pathways of Lyt subsets of T cells are more complex than originally proposed and that commitment to separate lines of differentiation may occur already at the level of immature, cortical thymocytes.