Bypassing LEC-mediated tolerance enables FH cells to acquire cytolytic and effector function leading to the development of autoimmune vitiligo. (A) FH or PD-1^−/− FH cells were transferred into tyrosinase⁺ mice left untreated or treated with blocking anti-PD-L1, or agonist anti-4-1BB and –OX40. Albino mice were infected with VACV-tyr. LNs were harvested 7 days after transfer and restimulated ex vivo. Numbers indicate the total percentages of FH cells that are negative, single, or double positive for CD107a, IFN-γ, or TNF-α. Data are representative of 4 to 11 mice per condition from 2 to 5 independent experiments. (B-E) FH or PD-1^−/− (▾) FH cells were transferred into untreated tyrosinase⁺ mice (•), PD-L1^−/− mice (■), or tyrosinase⁺ mice treated with agonist anti-4-1BB and –OX40 (▴). Mice were monitored weekly for the development of autoimmune vitiligo evidenced by (B,D) whisker or (C,E) coat depigmentation. Arrows point to whiskers (C) and areas of coat depigmention are outlined in white (D). (B,D) Data for vitligo scoring of whiskers is representative of 3 to 7 mice per condition from 2 independent experiment while (C,E) data for vitiligo scoring of the body is representative of 7 to 9 mice per condition from 2 to 3 independent experiments. (B) ***P < .005 (one-way ANOVA, Tukey posttest). (C) * indicates PD-L1^−/−tyrosinase⁺; #, anti-4-1BB and OX40 treated; z, PD-1^−/− FH T_CD8. z, #, *P < .05; ##, **P < .01, ***P < .005 (2-way ANOVA, Bonferonni posttest). Error bars (B-C), SEM.