Lack of IL-10 Release from Human Polymorphonuclear Leukocytes

PURPOSE: Polymorphonuclear leukocytes (PMNs) are the first line of cellular response for host defense during acute inflammation. The ability of PMNs to produce and release numerous pro-inflammatory cytokines is now estabilished and plays an important role in triggering and maintaining the inflammatory response. We studied the autocrine downregulation of this process by invesgating the potential production by human PMNs of the major anti-inflammatory cytokine, interleukine 10 (IL-10). METHODS: Human PMNs were isolated from the peripheral blood of health volunteers by using the modified boyum method. Human PMNs were incubated at 37 degrees Cwith and without formyl Met-Leu-Phe (fMLP) for 30 minute, 2 hours, 4 hours, and 20 hours. The level of IL-10 was determined in each of the cell-free supernatants by using the enzyme linked immunosorbent assay (ELISA) method. RESULTS: Non-stimulated PMNs generated 1.40 +/- 1.791pg/mL to 3.46 +/- 1.607 pg/mL of IL-10 over the time course. Stimulation with fMLP resulted in an increase in the constitutive PMN-derived IL-10 by 2.74 +/- 0.762 pg/mL, 1.27 +/- 0.262 pg/mL, 1.19 +/- 0.364 pg/mL, and 2.44 +/- 1.317 pg/mL at 30 min, 2 hr, 4 hr, and 20 hr after stimulation, respectively, but these increases were not statiscally significant. CONCLUSION: Human PMNs seem unable to induce release of the most potent anti-inflammatory cytokine, IL-10, and down-regulate inflammatory response due to the autocrine mechanism. This could partly account for the persistence of local inflammation, when PMNs are the main infiltrating cells.

Anti-inflammatory effects of IL-4 and IL-10 on Human Polymorphonuclear Leukocytes

Inflammatory responses are strictly regulated by coordination of pro-inflammatory and anti-inflammatory mediators. Interleukin-4 (IL-4) and interleukin-10 (IL-10) have typically the biologic anti-inflammatory effects on monocytes, but uncertain effects on polymorphonuclear leukocytes (PMNs). The PMNs are the first line of cellular response for host defense during acute inflammation. To modify hyper-inflammatory reaction with biologic anti-inflammatory mediators, we have determined the biologic anti-inflammatory activities of IL-4 and IL-10 on human PMNs. Human PMNs were pretreated with IL-4 or IL-10 and then stimulated with formyl methionyl leucyl phenylalanine (fMLP) for times indicated. The level of H2O2, interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-alpha) were determined in the each cell free supernatants. fMLP plays the role of a typical pro-inflammatory agent and, at least in determined conditions, down-regulated TNF release. IL-4 acts as an anti-inflammatory mediator but IL-10 did not show its anti-inflammatory activities on fMLP-stimulated human PMNs. IL-4 and IL-10 have different anti-inflammatory mechanisms. Perhaps, IL-10 needs co-factors to act as an anti-inflammatory mediator.