Chronic Immune Activation in Systemic Lupus Erythematosus and the Autoimmune PTPN22 Trp620 Risk Allele Drive the Expansion of FOXP3+ Regulatory T Cells and PD-1 Expression by Ferreira, RC, Dopico, X, Oliveira, JJ, Rainbow, DB, Yang, JH, Trzupek, D, Todd, SA, McNeill, M, Steri, M, Orrù, V, Fiorillo, E, Crouch, DJM, Pekalski, ML, Cucca, F, Tree, TI, Vyse, TJ, Wicker, LS, Todd, JA