CD274 and rheumatoid arthritis: In human, the role of PD-1/PD-L1 pathway has been observed in various autoimmune diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), and Type 1 diabetes mellitus (T1DM) [24], while little is known in autoimmune thyroiditis.