IMMUNO-LOCALIZATION OF TUMOR-NECROSIS-FACTOR AND ITS RECEPTORS IN TEMPORAL ARTERITIS

Temporal arteritis (TA) is an acute vasculitis characterised by destru ction of arterial architecture following infiltration of the arterial wall by macrophages, giant cells and lymphocytes. Using immunohistoche mical techniques, tumour necrosis factor (TNF) was demonstrated in up to 60% of the cells in all areas of inflamed arteries. More cells stai ning for TNF were detected in the intima and media of inflamed vessels than control uninflamed arteries (P < 0.003 and P < 0.001, respective ly). In TA, TNF was localised to giant cells and macrophages, suggesti ng that its predominant source is from the monocyte Lineage, but, occa sionally, TNF staining was found in areas infiltrated by T cells. Many endothelial cells also contained TNF, but there were no differences b etween the number of endothelial cells staining in inflamed and normal blood vessels. Of the two TNF receptors, the p75 receptor was sparsel y represented in the inflamed vessels in TA. By comparison, the p55 re ceptor was widely detected on endothelial cells and infiltrating monon uclear cells close to the internal elastic lamina (IEL). Endothelial c ells from normal Vessels also stained for both TNF receptors, but norm al smooth muscle cells in the vessel media expressed the p55 receptor, indicating that they are capable of responding to locally secreted TN F. Localisation of TNF receptors and TNF in close proximity to the IEL suggests that TNF could be involved in the leucocyte infiltration and arterial wall destruction characteristic of TA.