Human PD-1 (hPD-1), a member of the CD28 family, is a type 1 transmembrane immunoglobulin with a total length of 268 amino acids and its gene locates on the long arm of chromosome 2, the second largest chromosome, which indicates the protein may be cross-linked with many other gene products and involves in several important diseases such as inflammation, cancer, and autoimmune diseases [3]. The gene discussed is PDCD1; the disease is autoimmune disease.