in RA patients the count of CD34–THY1+ fibroblasts is threefold than that in OA, they generate a discrete perivascular zone, which surrounds the capillary structures in the synovium deep sublining layer, especially near aggregations of lymphocytes, and play an indispensable role in matrix infiltration, immune cell mobilization and osteoclast formation. This evidence concerns the gene THY1 and rheumatoid arthritis.