Cell-cell interactions in synovitis - Interactions between T lymphocytes and synovial cells

Mechanisms whereby T lymphocytes contribute to synovial inflammation in rhe umatoid arthritis are poorly understood. Here we review data that indicate an important role for cell contact between synovial T cells, adjacent macro phages and fibroblast-like synoviocytes (FLS). Thus, T cells activated by c ytokines, endothelial transmigration, extracellular matrix or by auto-antig ens can promote cytokine, particularly TNF alpha, metalloproteinase product ion by macrophages and FLS through cell-membrane interactions, mediated at least through beta -integrins and membrane cytokines. Since soluble factors thus induced may in turn contribute directly to T cell activation, positiv e feedback loops are likely to be created. These novel pathways represent e xciting potential therapeutic targets.