CTLA4 and rheumatoid arthritis: Highlighting its importance, several genes involved in IL-2/IL-2R signaling such as IL-2-IL21, CTLA4, IL2RA, IL2RB, CD83, PTPN2, and CCR6 were included in a list of RA risk gene loci identified to date in the transethnic genome-wide association study (GWAS) meta-analysis of RA [25,26].