Production of granulocyte colony-stimulating factor (G-CSF) by human cells: T lymphocyte-dependent and T lymphocyte-independent release of G-CSF by blood monocytes.

To evaluate the production of granulocyte colony-stimulating factor (G-CSF) by human immune and inflammatory cells, an assay specifically measuring G-CSF activity in the presence of other cytokines was developed which was based on the proliferation of 32Dcl cells induced by G-CSF. Successful use of the 32Dcl cells to specifically measure G-CSF activity required the selection of cells highly responsive to G-CSF and with reduced responsiveness to interleukin 2 (IL 2) by intermittent culture in medium containing G-CSF. Furthermore, the addition of exogenous IL 2 to standards and experimental samples was necessary to ensure that the concentration of IL 2 was similar in all samples, since IL 2 directly stimulated the proliferation of 32Dcl cells and increased their responsiveness to G-CSF. A variety of stimuli were found to induce G-CSF release by blood monocytes. Lipopolysaccharide and monocyte adherence appeared to directly stimulate G-CSF release, whereas stimulation of G-CSF release from monocytes by mitogenic lectins required the presence of T lymphocytes. In all cases, release of G-CSF was detectable as soon as 4 h after stimulation and was essentially complete after 48 h. These findings indicate that G-CSF release can be initiated by a variety of pathways, and therefore suggest that the production of this mediator may occur in the course of many immune and inflammatory reactions.