Protein tyrosine phosphatase PTPN22 in human autoimmunity.

The discovery that a single-nucleotide polymorphism (SNP) in lymphoid tyrosine phosphatase (LYP), encoded by the PTPN22 gene, is associated with type 1 diabetes (T1D) has now been verified by numerous studies and has been expanded to rheumatoid arthritis, juvenile rheumatoid arthritis (JRA), systemic lupus erythematosus, Graves' disease, generalized vitiligo and other human autoimmune diseases. In this paper, we discuss the association of PTPN22 with autoimmunity, the biochemistry of the PTPN22-encoded phosphatase, and the molecular mechanism(s) by which the disease-predisposing allele contributes to the development of human disease.