PRODUCTION OF INTERLEUKIN-6 BY GRANULOMAS OF GIANT-CELL ARTERITIS

IL-6 serum levels are increased in patients suffering from GCA, and th is cytokine may play a role in the systemic symptoms associated with t his disease. We analyzed by in situ hybridization and immunohistochemi stry whether IL-6 production originates from arterial gran ulomas in G CA. Seven arterial biopsy specimens taken from patients with histologi cally proved GCA were studied. IL-6 production was detected in all cas es at both the mRNA and the protein levels. IL-6-producing cells were distributed in the intima, in the media, and in the adventitia. Positi ve cells were clearly enriched in the media, however, and particularly in contact with the internal elastic lamina. The morphology of the IL -6-producing cells showed that they belonged to several cell populatio ns. In the media, most IL-6-producing cells were macrophages, whereas fibroblasts also produced IL-6 in the intima. Neither endothelial cell s nor giant cells were found to express the IL-6 gene. Increased IL-6 serum concentrations returned to normal levels in most patients after administration of corticosteroids, indicating that inhibition of IL-6 production by GCA granuloma cells may be one of the mechanisms of acti on of corticosteroids in this condition. Production of IL-6 in abnorma l arteries may thus participate to the systemic manifestations of GCA.