Detection and localization of cytokine immunoreactivity in retro‐ocular connective tissue in Graves' opthalmopathy

Abstract

Paracrine interactions between fibroblasts residing in the retro-ocular space and infiltrating lymphocytes/macrophages are thought to be of central importance in the pathogenesis of Graves' ophthalmopathy (GO). Although various roles have been suggested for interferon-gamma (IFN gamma), tumour necrosis factor-alpha (TNF alpha) and interleukin-1 alpha (IL-1 alpha) in GO, their actual presence in Graves' retro-ocular connective tissue has not been demonstrated. We examined surgical specimens obtained during orbital decompression from patients with severe GO (n = 6), and from normal individuals (n = 5), for the presence of IFN gamma, TNF alpha and IL-1 alpha. We used immunohistochemical methods on frozen tissue sections and primary fibroblast cultures, and sodium dodecylsulfate polyacrylamide-gel electrophoresis of tissue extracts and tissue culture supernatants. In addition, immunohistochemical staining of tissues for characterization of the mononuclear cell infiltrates was performed. Aggregates of mononuclear cells in retro-ocular connective and fatty tissue were found in five of six GO tissue specimens, but in none of the control specimens. We detected immunoreactivity for the three cytokines (IFN gamma, TNF alpha and IL-1 alpha) in the five GO tissue specimens that contained mononuclear cell aggregates. In addition, IL-1 alpha immunoreactivity was demonstrable in primary and subsequent GO fibroblast cultures and in their supernatants. In contrast, no immunoreactivity for any of these cytokines was detected in tissue specimens, primary cultures or culture supernatants derived from normal individuals. The presence of mononuclear cell infiltrates and associated immunoreactivity for IFN gamma, TNF alpha, IL-1 alpha in retro-ocular connective tissue derived from patients with GO suggests that the previously demonstrated in vitro functions of these cytokines may indeed be operative in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)