Alteration in the responsiveness to tumour necrosis factor-α is crucial for maximal expression of monocyte chemoattractant protein-1 in human neutrophils

We previously reported delayed expression of monocyte chemoattractant protein-1 (MCP-1) in human neutrophils cultured with a cytokine-rich crude supernatant of phytohaemagglutinin-stimulated peripheral blood mononuclear cells (PHA-sup). Tumour necrosis factor-α (TNF-α) contained in the PHA-sup played a key role in this event, but there appeared to be another factor(s) in the same supernatant that co-operated with TNF-α for maximal MCP-1 expression. In the present study, we reduced TNF-α concentrations in the PHA-sup to minimal levels using anti-TNF-α affinity columns (TNF-depleted-sup) and investigated the co-operation between TNF-α and TNF-depleted-sup. Nine hours of preincubation with TNF-depleted-sup altered the responsiveness of neutrophils to TNF-α and enabled TNF-α to increase the level of MCP-1 expression to a maximal level within 4 hr. The priming effect was not due to the increased expression of cell-surface TNF receptors. However, the activation of primed cells by TNF-α was clearly through TNF receptor-p55. Finally, the activity in the TNF-depleted-sup that co-operated with TNF-α was eluted at 60 000 MW on high-performance liquid chromatography-gel filtration. Thus, delayed neutrophil expression of MCP-1 is regulated by a cytokine-dependent mechanism that induces neutrophils to enter a 'mature' stage.