['The aims of this study are to test the ability of stromal cells from murine spleen to support hematopoiesis, to define the tissue source of precursors that seed these hematopoietic niches, and to determine the type of cells produced.', 'Cloned isolates of murine spleen stroma have been developed that support hematopoiesis. Analysis has been investigated in terms of tissue source of progenitors. Type and number of cells produced were analyzed by flow cytometry.', 'Hematopoietic precursors that seed cocultures exist in spleen and bone marrow (BM), but not thymus. Cell production is highest if overlay cells are enriched for hematopoietic precursors. BM contains more precursors than spleen, but the cell types produced are different. Cocultures established from spleen maintain a high proportion of a distinct class of dendritic-like cells produced in only low numbers in BM cocultures. These reflect the immature myeloid dendritic cell (DC) produced continuously in long-term spleen cultures established previously in this laboratory. Stroma-conditioned medium alone does not support DC development, but does support early outgrowth of myelomonocytic cells from precursors in both spleen and BM.'] Do splenic stromal niches support hematopoiesis of dendritic-like cells from precursors in bone marrow and spleen?