Separation of erythroid and granulocytic precursors based upon the expression of FC6 antigen

The authors have developed a γ2akappa mouse monoclonal antibody (FC6) against pre-B leukemia cells with chromosomal translocation t(1;19). By immunofluorescence, FC6 recognized ∼20% of fresh marrow mononuclear cells (NMC), but <1% of fresh blood erythrocytes, granulocytes, MNC, and platelets in normal adults. However, ∼50% of mitogen-stimulated blood T cells expressed FC6 antigen on day 3 and all hemopoietic cultured cell lines examined were FC6+ regardless of their cell lineages, suggesting the association of FC6 antigen expression with cellular proliferation. By immunoprecipitation analysis of radiolabeled membrane proteins of FC6+ cell lines, FC6 antigen was ∼90 Kd under reducing condition and similar to transferrin receptor. By using fluorescence activated cell sorter, three subpopulations of marrow NMC were fractionated: brightly FC6+ (3-10%), dimly FC6+ (4-16%) and FC6- (79-92%), Stem cell culture analysis of each fraction (Fx) indicated that almost all CFU-E and the majority of BFU-E were in the brightly FC6+ Fx while CFU-GM was mainly in the dimly FC6+ Fx. These results suggest that CFU-E/BFU-E and CFU-GM are separable based upon the expression of FC6 antigen