Lymphohematopoietic progenitors of normal mice.

We have identified and characterized the lymphohematopoietic progenitors in the bone marrow of normal mice using a single-step methylcellulose culture assay. Lineage-negative Ly-6A/E (Sca-1)+ progenitors isolated from normal mice were plated in methylcellulose culture containing steel factor (SF), interleukin-7 (IL-7), erythropoietin (Ep), and IL-11. After 16 to 17 days of culture, pre-B-cell-containing multilineage myeloid colonies can be microscopically identified; however, flow-cytometric analysis of individual colonies for B220-positive cells proved superior to in situ microscopic identification of lymphomyeloid colonies. Approximately 10% (6/66) of the mixed colonies without a conspicuous B-cell component had B220-positive cells. The single cell origin of the lymphomyeloid colonies was confirmed by micromanipulation. Although the combination of SF, IL-7, and Ep was sufficient to support formation of lymphomyeloid colonies, addition of IL-11, granulocyte colony-stimulating factor or IL-12 to the combination of SF, IL-7, and Ep increased the number of lymphomyeloid colonies. IL-1 alpha and IL-3 independently inhibited the expression of the B-lymphoid lineage when added to the combination of SF, IL-7, Ep, and IL-11. Approximately four times more lymphohematopoietic progenitors are present in normal mice than in mice treated with 5-fluorouracil.