TLR9 and type 1 diabetes mellitus: In addition to the observation that the Lyp variant diminishes IFN production and IFN responses upon TLR stimulation, thus predisposing individuals with the variant to uncontrolled infections, the increased TLR9 response leading to expanded T cell-independent IgM+ memory B cells that was observed in our study will propel future investigations into the relative contribution of PTPN22 function in the pathogenesis and progression of T1D.