Synergy between tumour necrosis factor α and granulocyte-macrophage colony-stimulating factor in neutrophil stimulation

Abstract

We have examined the interaction between the cytokines, granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor α (TNFα) on polymorphonuclear leukocyte (PMN) function and on PMN responses to further stimulation with formyl Met Leu Phe (fMLP). Incubation of PMN with TNFα (0.3 nM) and, to a lesser extent, with GM-CSF (1 nM) directly stimulated superoxide anion (O ⁻₂ ) generation and increased the response to subsequent stimulation of PMN by fMLP (100 nM). However, the combination of GM-CSF and TNFα did not result in increased O ⁻₂ generation and there was no synergistic effect of the combination of these cytokines on the priming of fMLP-induced O ⁻₂ generation. The combination of TNFα and GM-CSF did result in a striking synergism in the stimulation of PAF generation, and, whereas neither stimulus alone resulted in detectable PAF release, the combination elicited the release of significant levels of PAF. The observation of significant PAF release from PMN exposed to TNFα and GM-CSF indicates that overt neutrophil stimulation with phagocytic or soluble stimuli may not be required for expression of at least some of the PMN pro-inflammatory capacity.