Expression of antigens of the 'T200' family of glycoproteins on hemopoietic stem cells: evidence that thymocyte cell lineage antigens are represented on 'T200'.

A panel of monoclonal antibodies has been used to investigate the presence of antigens of the 'T200' family of cell surface glycoproteins on hemopoietic stem cells. As measured by spleen colony inhibition using CBA bone marrow, stem cells were shown to be antigenically heterogeneous with respect to 'T200' family antigens; greater than 60% loss of spleen colonies was observed with 74/8 and 30F11 monoclonal antibodies and with Ly5.1 alloantiserum, whereas little effect was observed with 30G12. Two of four monoclonal antibodies with specificity for B220 showed significant inhibition of spleen colony formation. Monoclonal antibodies against Mac-1, another family of cell surface glycoproteins, had little effect on stem cells. In general, a similar pattern of spleen colony inhibition was observed in CBA, BALB/c, and C57/BL/6 mice. Spleen colony inhibition did not correlate with antibody isotype or with antibody binding to thymocytes, B lymphocytes, macrophages, or platelets as determined by indirect radioimmunoassay. Cell lineage antigens held in common between thymocytes and stem cells were shown to be wholly represented on the T200 glycoprotein. Thus, the anti-stem cell activity in anti-thymocyte serum (ATS) was absorbed by BW5147 T200+ cells but not by a T200- variant. The results show that some antigens of the 'T200' family of cell surface glycoproteins defined with monoclonal antibodies are expressed on stem cells and that other T200 antigens represented in ATS but not as yet identified with monoclonal antibodies show T lineage restriction.