Production of IL-6 by T cells from the femoral head of patients with rapidly destructive coxopathy (RDC).

RDC is a syndrome with unknown etiology that causes rapid destruction of a hip joint. We have investigated the production of osteoclast-activating cytokines (IL-6, IL-1alpha and tumour necrosis factor-alpha (TNF-alpha)), interferon-gamma (IFN-gamma) and IL-8 by T cells in the affected joint. The level of IL-6 produced by the T cell lines (TCL) established from the femoral head was significantly higher than that from patients' or healthy donors' peripheral blood mononuclear cells (PBMC). IL-6 production by the TCL from synovial membrane or from patients' PBMC was also significantly higher than that from healthy donors' PBMC. IL-1alpha production by the TCL from the femoral head was significantly higher than any of the other groups when all the TCL were used for the analysis. TNF-alpha production was highest in the TCL from patients' PBMC. The levels of IFN-gamma or IL-8 were not significantly different among these four groups. The plasma levels of all these cytokines except for IFN-gamma, that was rather lower, in RDC patients were not significantly different from those in osteoarthrosis or trauma patients, or healthy donors. These results suggest that T cells at the affected femoral head, and also synovial membrane to some extent, are involved in bone resorption through the production of IL-6 and probably IL-1alpha in patients with RDC.