Direct activation of mast cells by prosthetic biomaterial particles

IL-4 is a mast cell and T cell produced immune cytokine that is important i n the regulation of macrophage function. IL-4 has also been implicated in t he induction of foreign body giant cell formation. In patients with long-te rm joint prostheses, a localized granulomatous inflammation develops in per iarticular tissues and other organs where phagocytosis of particulate mater ial from various prosthetic components takes place. In this study we used t he inflammatory lesions of the bone-implant interface as a model to investi gate the possible production, the frequency and the cellular source of IL-4 . 40 samples of the interface membrane obtained from 25 patients undergoing revision of clinically failed implants were analyzed by immunohistochemist ry. Cryostat sections were labeled with specific monoclonal antibodies to m ast cell products: IL-4, tryptase and the receptor c-kit (CD117). The study has identified a significant level of production of IL-4 by mast cells in all the cases analyzed. There was an apparent difference in the number of m ast cells in relation to the histological variants of the interface. The in crease in the number of mast cells and IL-4 production was more pronounced in cases with heavy macrophage infiltrate than those exhibiting a predomina nce of giant cells. The findings imply that the recruitment of mast cell an d IL-4 expression precede the granulomatous reaction and may have a role in the induction of a number of immunopathological changes related to mast ce ll activation by biomaterial particles. (C) 1998 Kluwer Academic Publishers .