Functional Assessment of Precursors from Murine Bone Marrow Suggests a Sequence of Early B Lineage Differentiation Events

AbstractMost lineage marker–negative (Lin−)TdT+ cells from murine marrow lack CD34 but display c-kit at low density as well as IL-7Rα and Flk-2/Flt-3 receptors. Single cells with these characteristics generated CD45RA+CD19− as well as CD19+ lymphocytes in culture. CD45RA+CD19− marrow cells were resolved into three nonoverlapping subsets. One subset, lacking DX5 and Ly-6C antigens, yielded CD19+ cells in culture. Further analysis demonstrated CD24 on most Lin−TdT+ cells and all CD45R+CD19−DX5−Ly-6C− cells. Mac-1/CD11b was absent from these two subsets of B lineage precursors, while IL-7Rα was retained during subsequent differentiation to a CD19+ and stromal cell–independent stage. These findings contrast with previous descriptions of B lymphocyte precursors and suggest a sequence of early differentiation events