Increased DR antigen expression by committed hemopoietic progenitor cells but not primitive progenitor cells in chronic myeloid leukemia.

We used a complement-dependent cytotoxic assay to study the expression of DR antigens by hemopoietic progenitor cells derived from normal marrow and from the blood of patients with chronic phase chronic myeloid leukemia (CML). Almost all normal and CML day-12 granulocyte-macrophage colony-forming cells (d12 GM-CFC) and erythroid burst-forming units (BFU-E) expressed DR antigens. A primitive progenitor cell, the "blast colony-forming cell" (Bl-CFC), also expressed DR antigens whether derived from normal marrow or CML blood. The expression of DR antigen by normal and CML Bl-CFC was similar but the density of DR antigens on CML d12 GM-CFC and BFU-E was much greater than that of their counterparts from normal marrow. The similarity in DR antigen density on normal and CML Bl-CFC means that purging of CML marrow using a DR-specific antibody would not select in favor of normal cells and thus would not be useful in an autograft setting.