Differentially expressed genes between a high inflammation and a low inflammation group in RA included genes specific for T- and B-cells such as CD20, CD9, CD69, T cell receptor β and γ chain, proteases MMP1, MMP3, chemokines IP-10, CXCR4, SDF1, transcription factors STAT-1 and c-fos, and cytokines/cytokine receptors IL-15, IL-6Rα, and IL-6Rβ. Here, IL15 is linked to rheumatoid arthritis.