Background
Recent evidence suggests an important role for IL-7 in the pathogenesis of rheumatoid arthritis (RA) and a therapeutic potential for IL-7 blockade [1]. IL-7 is produced by synovial stromal cells (StrC) in RA but is barely detectable in osteoarthritis [2]. Our published data showed reduced production of IL-7 by bone marrow (BM) StrC and reduced levels of circulating IL-7 in RA compared with health [3]. IL-7 was also detected in synovial tissue in active RA but levels were below detection in clinical remission. These conflicting observations suggest that the regulation of IL-7 expression is tightly controlled at the level of tissue specificity. To support this hypothesis, we showed that several cytokines have a different effect on IL-7 production in BM StrC, epithelial cells from the liver and gut. This work aims at identifying the factors that regulate IL-7 production in StrC isolated from synovial tissue of RA patients.