The role of PTPN22 risk variant in the development of autoimmunity: finding common ground between mouse and human

The PTPN22 1858T variant was among the first single nucleotide polymorphisms to be associated with multiple autoimmune diseases. Lymphocyte tyrosine phosphatase, a coding variant within the tyrosine phosphatases, is known to participate in AgR signaling; the impact of this variant on the immune response and its role in the development of autoimmunity have been a focus of study. These studies used a series of approaches, including transfected cell lines, animal models, and primary human lymphocytes, and identified multiple alterations in cell signaling and function linked to the PTPN22 variant. Conflicting findings led to questions of how best to study the role of this variant in human autoimmunity. In this review, we discuss these differences and the factors that may account for them, as well as show how an integrated approach can lead to a more complete understanding of the mechanisms that promote autoimmunity in the context of the PTPN22 1858T risk variant.