Augmentation and suppression of TNF release from macrophages by inflammatory polymorphonuclear leukocytes

It is known that polymorphonuclear leukocytes (PMNs) emerge first in local inflammatory sites, and then they are followed and scavenged by macrophages. We focused on the effect of PMN on tumor necrosis factor (TNF) release activity of macrophages, which is viewed as a possible indicator of the status of macrophage activation. One day after macrophages were cultured with fresh, intact murine PMNs which were induced with sodium casein, the release of TNF triggered by lipopolysaccharide (LPS) was augmented by low concentrations of PMNs, but suppressed by their high concentrations. When the PMN samples were fractionated into soluble and insoluble fractions, the augmenting and suppressing activity was partitioned; the relatively high concentrations of soluble fraction showed the suppressive effect whereas the insoluble fraction in lower concentrations showed augmentation. The suppressive activity was stable at 100 C, but the filtrates of the soluble fraction with membranes having cut-offs of 5,000 or 10,000 were not suppressive at all, suggesting the suppression is not due to low molecular compounds. It was also suggested that the suppressive effect for TNF release was not due to contaminating LPS or transforming growth factor-beta. Inflammatory processes may thus be positively and negatively controlled by a quantitative factor of initial PMN populations by regulating the TNF release activity of the subsequent macrophages.