Effect of neutralizing agents against IFNγ, TNFα, and GM-CSF on PMN survival, activation, and function in the presence of supernatants from cytokine-activated NK cells. PMNs were cultured in the absence or presence of supernatants from unstimulated (NK sup) or cytokine-activated NK cells for 18 to 24 hours and compared with the control medium (Med) and PMNs treated with cytokines alone. Monoclonal anti–human GM-CSF antibody (20 μg/mL, αG), purified anti–human IFNγ antibody (20 μg/mL, αI) and soluble TNF receptor (1 μg/mL, αT) were added to PMN cultures in the presence of supernatants from cytokine-activated NK cells in different combinations. Quantitative representation of (A-B) percentage of apoptotic PMNs (n = 4), (C-D) fold increase in CD11b expression (n = 4), (E-F) CD62L expression on the surface of PMNs (n = 4), and (G) percentage of phagocytosing PMNs (n = 1). Fold increase was calculated as MFI of CD11b on PMNs for different conditions divided by the MFI of PMNs when cultured alone (control medium; Med). Results are expressed as mean ± SEM. *P < .05; **P < .01; ***P < .001.