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Granulocytic colony formation in agar occurred spontaneously in primary cultures of normal or leukemic human bone marrow cells. Spontaneous colony formation was concentration dependent, and the threshold for colony formation varied with marrow cells from various diseases. When marrow cells were cultured at subthreshold concentrations, colony formation by both ncrmel and leukemic cells required stimulation by an exogenous source of colony-stimulating factor (CSF). Spontaneous colony formation was due to the endogenous formation of CSF by colony-stimulating cells which could be separated from colony-forming cells by density gradient centrifugation. The CSF produced by colony-stimulating cells in human hematopoietic tissues was antigenically cross reactive with human urine CSF. In normal and leukemic blood cell populations fractionated with density gradient centrifugation and edherenee columns, colony-stimulating cells were actively adherent and of light to intermediate density. Colony-stimulating activity correlated with monocytes and not polymorphs or lymphocytes in these fractions.
Moore et al. (Thu,) studied this question.