Macrophage progenitors from mouse bone marrow and spleen differ in their expression of the Ly-6C differentiation antigen.

Using mAb and magnetic and fluorescence-activated cell sorting, together with culturing in semisolid culture medium, we show that essentially all splenic macrophage progenitors are Ly-6ChiMac-1-. By contrast, bone marrow macrophage progenitors were more heterogeneous in Ly-6C expression, the majority being restricted to the Ly-6CdimMac-1- and the Ly-6C-Mac-1- subsets. These findings provide immunophenotype evidence that macrophages in the spleen and bone marrow arise from different progenitors.