While there is a relative paucity of data regarding the exact nature and role of p-STAT5, compared to, for example, the role of p-STAT3 in RA the results of 3 recent studies lends support to a role for p-STAT5 in RA which can be summarized as follows: (1) RA synovial fibroblasts synthesized only low levels of constitutive CCL13/monocyte chemotractant protein-4. The gene discussed is CCL13; the disease is rheumatoid arthritis.