Autoreactive T cell-mediated inflammation induces CXCR3 expression by ICOS⁺ T_reg cells prior to T1D onset.

Cell suspensions of pancreas and draining LN from 4 week old (A, B) WT and (B) ICOS^-/- BDC2.5 mice were assessed for the frequency of CXCR3⁺ cells and levels of CXCR3 expression (MFI) between the ICOS⁺ and ICOS^- subsets of T_reg cells. (C and D) NOD.TCRα^-/- mice received MACS sorted BDC2.5 CD4⁺CD25⁺ (T_reg, 0.75X10⁵) or CD4⁺CD25^- (T_eff, 7.5X10⁵) cells alone or at the indicated T_reg/T_eff cell ratios. When the T_eff cell recipient mice displayed hyperglycemia (>33mmol/L), mice were sacrificed and expression of IFN-γ by T_eff cells (C) and CXCR3⁺ percent cells among the ICOS⁺ T_reg cell subset were assessed. (E) NOD.TCRα^-/- mice received the indicated ratios of FACS-sorted Thy1.2⁺ T_reg cells to 7.5X10⁵ BDC2.5 Thy1.1⁺ CD4⁺Foxp3^- T_eff cells. After 14 days, the Thy1.2 (tT_reg) and Thy1.1⁺ (pT_reg) subsets of ICOS⁺ T_reg cells were compared for percent CXCR3⁺ cells. (n = 4, peri LN = pooled axial, brachial and inguinal peripheral lymph nodes).