Jagged-1^hi or Delta-1^hi thymic stromal cell populations can trigger acquisition of Thy-1 and loss of B220

Effects of endogenous Notch ligands Jagged-1 and Delta-1 on maturation markers in adult mouse lymphocytes were checked in vitro on putative thymocyte precursors from bone marrow and on DN3 cells from the thymus. Both populations were cocultured with stromal cells (Small M, Histochem Cell Biol 2005;123:513) naturally expressing high levels of either Jagged-1 or Delta-1. Initially the bone marrow cells were Thy-1.2^neg while the majority were B220^hi. These trends were reversed by culture on both the Jagged-1^hi and Delta-1^hi monolayers. Then DN3 thymocytes were cultured with stroma expressing these two ligands and the T cell receptor β chain was expressed more clearly after coculture on Delta-1^hi stroma. These findings indicate that stromal cells with endogenous Jagged-1 as well as Delta-1 could initiate early changes toward T cell commitment while Delta-1 favored later αβ-TCR development.