Rheumatoid arthritis is a multifactorial disease characterized by chronic inflammation of the joints. Both genetic and environmental factors are involved in the pathogenesis leading to joint destruction and ultimately dis-ability. In the inflamed RA joint the synovium is highly infiltrated by CD4 + T cells, B cells and macrophages, and the intimal lining becomes hyperplastic owing to the increased number of macrophage-like and fibro-blast-like synoviocytes.