The expression of histocompatibility-2 antigens on hemopoietic stem cells

Antisera directed against histocompatibility-2 antigens of the mouse suppress the formation of spleen colonies by pluripotent hemopoietic stem cells. Of antisera which are specific for subregions of the H-2 complex, only those which contain anti-H-2K or anti-H-2D activity are effective. Specific anti-Ia sera do not react with the stem cell. If the titer of the CFU-s suppressive effect of the antisera is compared to their toxicity to spleen lymphocytes, it can be concluded that CFU-s express antigens in the same density as spleen lymphocytes. The amount of H-2 antigens expressed on the surface of CFU-s is independent of its rate of proliferation.