Figure 3. LCMV-induced upregulation of PD-L1 in prediabetic NOD mice prevents the expansion of IGRP-specific CD8⁺ T cells and delays the onset of T1D.

(A) Different siRNAs specific for PD-L1 were assessed for efficacy by infection of NOD splenocytes for 24 hours with LCMV in vitro (MOI, 1) after transfection with different siRNAs (in duplicate). Shown is inhibition of PD-L1 upregulation, calculated as the percentage of PD-L1^hi cells in populations infected with LCMV and transfected with siRNA relative to the percentage of PD-L1^hi cells in the population infected with LCMV and transfected with scrambled-sequence siRNA, ± SD for duplicate samples. (B) Percentage of PD-L1^hi cells over time in the pancreatic LN and spleen of individual NOD mice infected at 9 weeks of age with LCMV and simultaneously injected with cationic vehicle alone or containing 150 μg PD-L1 siRNA 76238, as measured by flow cytometry. (C) Percentage of IGRP-specific CD8⁺ T cells in the pancreatic LN and spleen of individual 12-week-old NOD mice injected 21 days previously with cationic vehicle alone and left untreated or simultaneously infected with LCMV (green inverted triangles) or injected 21 days previously with cationic vehicle containing PD-L1 siRNA 76238 and simultaneously infected with LCMV (white inverted triangles), as measured by flow cytometry after staining with NRP-V7 tetramer. In B and C, symbols represent individual values, and horizontal lines denote mean. (D) Cumulative diabetes incidence over time in NOD mice injected at 9 weeks of age with cationic vehicle alone and left untreated or simultaneously infected with LCMV or injected 21 days previously with cationic vehicle containing PD-L1 siRNA 76238 and simultaneously infected with LCMV. *P < 0.05, **P < 0.005, ***P < 0.001.