Infected patients are likely to have increased levels of tumor necrosis factor-alpha (TNF-alpha) and may be treated with recombinant human granulocyte colony-stimulating factor (G-CSF). Recombinant human TNF-alpha activates polymorphonuclear neutrophil (PMN) inflammatory activity. We examined the effect of exposure to TNF-alpha and G-CSF alone and in combination on PMN apoptosis, receptor expression, phagocytosis, and bactericidal function. The results were compared to those obtained with a promoter of PMN apoptosis, cycloheximide. After 24 hr, 27% of PMNs were nonapoptotic, and TNF-alpha (1 unit/ml) showed no change. Cycloheximide (10 micrograms/ml) decreased the number of nonapoptotic cells to 10% of the initial PMN. In contrast, G-CSF (30 ng/ml) decreased apoptosis (57% nonapoptotic PMN after 24 hr). Both G-CSF and TNF-alpha (but not cycloheximide) induced preservation of PMN Fc gamma RIII (467% and 167% of 24-hr controls, respectively) and beta 2-integrin expression (150% and 168% of 24-hr controls, respectively). G-CSF (but not TNF-alpha or cycloheximide) stimulated expression of Fc gamma RI (191% of 24-hr control) and Fc gamma RII (267% of 24-hr control). G-CSF (but not TNF-alpha) maintained the ability of PMN to ingest and kill opsonized Staphylococcus aureus. TNF-alpha decreased the effect of G-CSF on apoptosis, expression of Fc gamma RIII and Fc gamma RI, and bactericidal function. Thus, TNF-alpha promoted expression of Fc gamma RIII and beta 2-integrin receptors, which are important for phagocytic activity, and G-CSF diminished apoptosis, increased Fc gamma receptor expression, and maintained bactericidal function. TNF-alpha counteracted some effects of G-CSF. Interactions of these cytokines in vivo serve to regulate the PMN inflammatory response and bactericidal capacity.