MHC class II and c-kit expression allows rapid enrichment of T-cell progenitors from total bone marrow cells

T-cell progenitors in the embryonic bone marrow express the tyrosine kinase receptor c-kit, RR5, an anti-MHC class II beta chain monoclonal antibody, subdivides this c-kit positive population. Intrathymic transfer experiments showed that most of the T-cell progenitors belong to the MHC class II+/c-k it(+) bone marrow population in the embryo and young adult. On transplantat ion, these hone marrow progenitors lose this expression and differentiate i nto CD4 CD8 T lymphocytes, In contrast, erythroid progenitors are restricte d to the MHC class II-/c-kit(+) population. The MHC class II/c-kit(+) pro-T cells are metabolically active, because they stain brightly with rhodamin 123, Their cyclin A and B expression level suggests that they are in the mi totic phase of the cell cycle. Thus, we define an easy sorting protocol, wh ich allows enrichment of T-cell progenitors from total bone marrow hemopoie tic cells. (C) 2000 by The American Society of Hematology.