CD4 and autoimmune disease: Post-translational modifications of CD4 T cell epitopes had been well-established in other autoimmune diseases, for example, conversion of arginines to citrullines by peptidylarginine deiminases (PADs) in rheumatoid arthritis (34–37) and of glutamines to glutamic acids by tissue transglutaminase (TG) in celiac disease (38).