HLA antigens expressed on human pluripotent hemopoietic precursors in vitro (CFUMIX).

The human major histocompatibility antigen HLA, plays an important role in transplantation. To ascertain the expression of the antigens of HLA-A and -B loci on the surface of human pluripotent hemopoietic progenitors (CFUMIX), the cytotoxic effect of specific anti-HLA sera was examined. Anti-HLA sera and complement formed fewer colonies from CFUMIX in a culture medium than the controls which were treated with autologous serum. In our experiments, the HLA antisera killed also T cells that carry the surface antigen. Then the influences of T cells on mixed colony formation were examined. No reduction of colony formation was observed from the cell suspension in which T cells were depleted by treatment of monoclonal antibody OKT3. These results indicated that CFUMIX expressed HLA antigens on their surface.