PDCD1 and autoimmune disease: Numerous pieces of evidence show that the PD-1 axis plays an significant role in autoimmune disorders, including inflammatory bowel disease (IBD), systemic lupus erythematosus (SLE), Type 1 diabetes (T1D), systemic vasculitis, myositis, autoimmune encephalomyelitis, autoimmune hepatitis, Behcet’s disease, myasthenia gravis, autoimmune uveitis, Sjogren’s syndrome, and ankylosing spondylitis (14, 57–61).