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
.