PTPN22 and invasive bacterial disease.

Vang et al.1 recently reported that the protein tyrosine phosphatase PTPN22 Trp620 variant is a gain-of-function mutant, resulting in increased PTPN22 phosphatase activity in T cells. This variant is associated with susceptibility to multiple autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus and autoimmune thyroid disease2, 3, 4, 5, 6. Based on the observation that Trp620 downregulates T cell responses1, we hypothesized that the PTPN22 R620W polymorphism may be associated with susceptibility to invasive bacterial infection.