Biologic properties in vitro of a recombinant human granulocyte- macrophage colony-stimulating factor

Recombinant human granulocyte-macrophage colony-stimulating factor (rH GM-CSF) was purified to homogeneity from medium conditioned by COS cells transfected with a cloned human GM-CSF cDNA and shown to be an effective proliferative stimulus in human marrow cultures for GM and eosinophil colony formation. The specific activity of purified rH GM- CSF in human marrow cultures was calculated to be at least 4 X 10(7) U/mg protein. Clone transfer experiments showed that this proliferation was due to direct stimulation of responding clonogenic cells. Acting alone, rH GM-CSF did not stimulate erythroid colony formation, but in combination with erythropoietin, increased erythroid and multipotential colony formation in cultures of peripheral blood cells. rH GM-CSF had no proliferative effects on adult or fetal murine hematopoietic cells, did not induce differentiation in murine myelomonocytic WEHI-3B cells, and was unable to stimulate the survival or proliferation of murine hematopoietic cell lines dependent on murine multi-CSF (IL 3). rH GM- CSF stimulated antibody-dependent cytolysis of tumor cells by both mature human neutrophils and eosinophils and increased eosinophil autofluorescence and phagocytosis by neutrophils. From a comparison of these effects with those of semipurified preparations of human CSF alpha and -beta, it was concluded that rH GM-CSF exhibited all the biologic activities previously noted for CSF alpha.     

The antiproliferative effect of calcitriol on human peripheral blood mononuclear cells

Activation of lymphocytes leads to the expression of receptors for the calcitropic hormone calcitriol [1,25(OH)2D3], and calcitriol is a potent inhibitor of interleukin-2 (IL-2) and of lymphocyte proliferation. We used peripheral blood mononuclear cells (PBM) activated in vitro with phytohemagglutinin to study 1) the relationship between 1,25(OH)2D3 receptor expression, IL-2 production, and 1,25(OH)2D3-induced inhibition of PBM proliferation in connection with the cell cycle; 2) the effect of 1,25(OH)2D3 on PBM activation and on the expression of activation-related molecules including the IL-2 receptor, and 3) the role of calcium in the antiproliferative effect of the hormone. 1,25(OH)2D3 receptor expression occurred when PBM entered the G1a phase of the cell cycle. The concentration of the receptor protein reached a peak at G1b and declined during the S phase. 1,25(OH)2D3 inhibited cell proliferation by blocking PBM at the G1a-G1b border. The antiproliferative effect of calcitriol was not caused by hormonal interference with the calcium-dependent activation process nor with the expression of activation-related molecules including the IL-2 receptor. Moreover, this effect was not influenced by extracellular calcium, suggesting that the hormonal action cannot be due to calcium translocation. These findings support the contention that 1,25(OH)2D3-induced inhibition of PBM proliferation is mediated through selective inhibition of IL-2 production.