Effects of anti-myeloid antibodies on the generation of hematopoietic colony-forming units in long-term bone marrow culture

We have prepared and characterized several monoclonal antibodies (MoAbs), PM-18 (CD 15),AML-2-23 (CD 14), and AML-1-99 (no cluster designation) reactive with antigens expressed on myeloid cells. Previous studies using complement-dependent lysis have determined the reactivity of these MoAbs with hematopoietic cells in vitro. PM-81 and AML-2-23 react with variable percentages of CFU-GM but not BFU-E or CFU-Mix. AML-1-99 reacts with greater than 90% of CFU-GM. CFU-E, and CFU-Mix. In order to determine the reactivity of these MoAbs with the bone marrow-derived precursors of in vitro colony-forming cells we have performed complement-dependent lysis and fluorescence activated cell sorting of bone marrow cells followed by long-term culture of surviving or sorted cells. Bone marrow cells from four normal subjects were subjected to various combinations of MoAbs and complement and assayed for residual colony-forming cells. Total surviving cells were then placed in flasks which contained a monolayer of irradiated bone marrow-derived adherent cells previously obtained from allogeneic donors. The cultures supported production of non-adherent colony-forming cells for up to 6 weeks as determined by serial in vitro colony-forming assays in methylcellulose. Cultures treated with one, two or three MoAbs and complement demonstrated variable reductions in colony-forming cells at the initiation of the experiments. However, cumulative production of colony-forming cells in anti-MoAb-treated cultures was usually at least as great as in control cultures.(ABSTRACT TRUNCATED AT 250 WORDS)