Surface phenotypes of freshly isolated or cultured BM cells. Freshly isolated mouse BM cells or BM cells cocultured on NIH3T3 cells were subjected to two-color flow cytometry analysis. Myeloid cells were simultaneously detected by anti-Mac1 antibody, and B-lineage cells were stained for a CD45RA marker. Quadrants are indicated to show levels of background stainings observed with appropriate irrelevant control antibodies.