A monoclonal antibody that identifies human peripheral blood monocytes recognized the accessory cells required for mitogen-induced T lymphocyte proliferation

These studies were carried out to evaluate the functional characteristics of the cells identified by a monoclonal anti-human mononuclear phagocyte (M∅) antibody, 63D3. This antibody reacts specifically with all human peripheral blood M∅ and not with normal human peripheral blood T or B cells. By using the fluorescence-activated cell sorter, human peripheral blood mononuclear cells (PBM) were sorted into 63D3-positive and 63D3-negative populations. Cell volume analysis indicated that 63D3-negative cells were identical to the nonadherent cells (NAC) in PBM, whereas 63D3-positive cells had a bimodal size distribution comparable to glass-adherent cells (AC). Neither 63D3-negative cells nor NAC were able to proliferate in response to mitogenic stimulation, whereas co-culture with either mitomycin C-treated AC or 63D3-positive cells restored mitogen responsiveness. Thus, the 63D3-positive population contains the relevant accessory cell required for mitogen-induced human lymphocyte proliferation.