THYMIC DENDRITIC CELL PRECURSORS - RELATIONSHIP TO THE T-LYMPHOCYTE LINEAGE AND PHENOTYPE OF THE DENDRITIC CELL PROGENY

Successive T-precursors isolated from adult mouse thymus were examined for their developmental potential, by transfer to irradiated Ly 5-dis parate recipients. The earliest, ''low CD4'' precursors formed T, B, a nd dendritic cells (DC), but not myeloid cells, in accordance with ear lier studies. Surprisingly, the next downstream CD4(-)8(-)3(-)44(+)25( +) precursor population still formed DC as well as T cells although it no longer formed B or myeloid cells. Further downstream, the CD4(-)8( -)3(-)44(-)25(+) population formed only T cells. The thymic and spleni c DC progeny of the early thymic precursors all expressed high levels of CD8 alpha, in contrast with normal splenic DC and the splenic DC pr ogeny of bone marrow stem cells, which consisted of both CD8(-) and CD 8(+) DC. A common precursor of T cells and of a subclass of DC is prop osed, with CD8 alpha as a marker of the lymphoid-related DC lineage.