Polymorphonuclear leukocyte inhibition of monocytes/macrophages in the foreign body reaction

Abstract

The effect of polymorphonuclear leukocytes (PMNs) on the subsequent chronic phase macrophage‐mediated foreign body reaction has not been previously investigated. Furthermore, while monocyte/macrophage‐produced cytokines such as GM‐CSF, G‐CSF, or IL‐1β have been shown to increase PMN survival in vitro , few studies have examined the impact of directly cocultured monocytes/macrophages on PMN viability. To this end, we used our established in vitro system of interleukin (IL)‐4‐induced monocyte‐derived macrophage fusion to examine the role of PMNs in the subsequent foreign body reaction. Monocytes were directly cultured with PMNs for 3 days before the addition of IL‐4 to induce monocyte‐derived macrophage fusion to facilitate foreign body giant cell (FBGC) formation by days 7 and 10 of culture. Optical microscopy was used to quantitatively determine adherent monocyte density, percent macrophage fusion, and FBGC density. A colorimetric MTT assay was used to assess PMN viability for direct cocultures of monocytes/macrophages and PMNs. Our results strongly suggest that the presence of PMNs inhibit IL‐4‐induced macrophage fusion and FBGC formation. Additionally, our findings demonstrate that cocultures containing PMNs and monocytes/macrophages increases PMN survival with respect to PMN‐only cultures in vitro . © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010