TYK2 and rheumatoid arthritis: A genome-wide association study (GWAS) meta-analysis, and other studies, found that the TYK2 P1104A variant was protective against multiple autoimmune diseases, including multiple sclerosis (MS), psoriasis, inflammatory bowel disease (IBD), ankylosing spondylitis, rheumatoid arthritis (RA), systematic lupus erythematosus (SLE), and type-I diabetes (T1D), without increased susceptibility to infection (see Table 1) [31,32,33,35].