PTPN22 in autoimmunity: different cell and different way.

The tyrosine phosphatase PTPN22 regulates T cell receptor signaling. In this issue of Immunity, Wang et al. (2013) show that in myeloid cells PTPN22 potentiates TLR-induced type I interferon production and that autoimmunity-associated allele PTPN22W encodes a reduced-function variant.