CD226 and rheumatoid arthritis: Moreover, single-nucleotide polymorphisms (SNPs) in the DNAM-1 gene have been associated with increased vulnerability to autoimmune diseases, such as MS, rheumatoid arthritis (RA), type 1 diabetes (T1D), systemic lupus erythematosus (SLE), primary immune thrombocytopenia, juvenile idiopathic arthritis and autoimmune thyroid disease [22,23,24,25].