In addition, genetic studies revealed that there is an association between PDCD-1 gene polymorphism and susceptibility to autoimmune diseases, such as systemic lupus erythematosus (SLE) [10, 11], rheumatoid arthritis [12, 13], multiple sclerosis [14], and diabetes mellitus [15, 16]. This evidence concerns the gene PDCD1 and rheumatoid arthritis.