Relative cytokine and cytokine inhibitor production by mononuclear cells and neutrophils.

Mononuclear cells represent the major source of cytokines in blood; however, it has been postulated that neutrophils may produce and/or release modest amounts of cytokines. In this study, we compared the production of cytokines and cytokine inhibitors in lipopolysaccharide (LPS)-stimulated whole blood, peripheral blood mononuclear cells (PBMCs), and neutrophils (PMNs) separated by density gradient centrifugation. Contamination of PBMCs in the isolated PMNs was less than 0.1% as determined by morphological analysis and flow cytometry. LPS (50 ng/mL) induced a strong increase of the proinflammatory cytokines tumor necrosis factor, interleukin (IL)-1beta, IL-8, and IL-6 in whole blood. In the isolated cell preparations, proinflammatory cytokine production was significantly greater in the PBMCs compared with the PMNs. On a per cell basis, PMNs produced less than 1.5% of these cytokines compared with PBMCs. For cytokine inhibitors, TNF-soluble receptor type II and IL-1 receptor antagonist were increased by LPS stimulation in whole blood, PBMCs, and PMNs. On a per cell basis, LPS-induced TNF-soluble receptor type II and IL-1 receptor antagonist production by PMNs was 9.8% and 15.4% of those of PBMCs, respectively. These data show that a highly purified population of PMNs makes a relatively minor to nonexistent contribution to the production of proinflammatory cytokines.