A volcano plot depicting the proteins' expression levels shows that six proteins were significantly up-regulated in the RA patient group, including IL-2, IL-5, IL-11, IL-17, TNF-β and CTLA-4, while IL-8, PD-L2 , B7-2 was significantly down-regulated (logFC>log2(1.2), p-value<0.05) (Figures 1A and 1B, and Figure2). The gene discussed is PDCD1LG2; the disease is rheumatoid arthritis.