HIM₁ and HIM₄, two monoclonal antibodies potentially useful for autologous bone marrow transplantation in chronic myelogenous leukemia

Abstract

We developed two complement-fixing MoAbs HIM₁ and HIM₄ (murine) that were specifically reactive with chronic myelogenous leukemia (CML) cells. They were capable of fixing human or rabbit complement and suitable for CML cells purging of remission marrow from CML patients. HIM₁ reacted with majority leukemic cells from 7 out of 10 CML patients by complement-mediated cytotoxicity (CMC) assay (positive cells 80%–90%), HIM₄ reacted with majority CML cells from 4 out of 5 CML by CMC assay (positive cells 80%–90%). Treatment with HIM₁ or HIM₄ and human C′ was capable of lysing 97% of K562, U937, HL-60 and CML cells in a 20 fold excess of unrelated cells by indirect FITC+EB stain. Using limited dilution culture, incubation with HIM₁ and C′ produced 1.5 logs inhibition of growth in K562 cells, and 1.9 logs in U937 cells, and with HIM₄ and C′ produced 2.9 logs inhibition in HL-60 cells and 3.0 logs in U937 cells. Both MoAbs cocktail was shown 1.8 logs in K562 cells and 3.2 logs in U937 cells. They were no suppression on the growth of CFC-GM.