Immunological separation of two CFU-GM subsets showing different responsiveness to T-cell derived growth factors.

Among human myeloid precursors two different subpopulations can be distinguished: type-2 CFU-GM, more differentiated, reacting to the monoclonal antibody DSl-1 and type-1 CFU-GM, more immature, negative to the DSl-1. Using this monoclonal antibody, type-1 and type-2 CFU-GM were fractionated and separately grown in the presence of T-cell derived CSFs, i.e., conditioned medium of PHA-stimulated T-lymphocytes (PHA-Ly) and the supernatant of Il-2-dependent normal T-cell lines (TC-SN). The supernatants of two neoplastic non-T cell lines, TPA-30-1 and GCT, were used as control. PHA-Ly and TC-SN had a very weak activity on type-2 CFU-GM (18 and 14% of colony growth, compared to control). However, they potently stimulated type-1 CFU-GM (84 and 68.5% of colony growth, compared to control). The restricted activity of T-cell derived CSFs on early myeloid progenitors is therefore demonstrated. Our results also show that CFU-GM with different responsiveness to growth factors can be physically separated on the basis of their reactivity to monoclonal antibody DSl-1.