Treg-B are sensitive to FasL-induced apoptosis. (A) IPA comparing Treg-B isolated from AA patients (n = 3) to Treg-B isolated from HD (n = 2) shows the ranking of top 10 significant upregulated canonical pathways by −log (P value). Red indicates positive z score; gray indicates zero z score, and blue indicates negative z score. (B) IPA analysis on the RNA sequencing data shows the ranking of top 10 canonical pathways by −log (P value) in AA Treg-B (n = 3) compared with AA Treg-A (n = 3). Significant upregulation of Fas in 3 out of 10 pathways is indicated. (C) Volcano plot shows the significant differential expressed genes in death receptor signaling (red) and the upregulation of homing receptors (yellow) in Treg-B isolated from AA patients (n = 3) as compared with Treg-A (n = 3). (D) The percentage of early (Viability Dye eFluor 780⁻ Annexin V⁺) and late (Viability Dye eFluor 780⁺ Annexin V⁺) apoptotic cells in Treg-A and Treg-B before and after treatment with 5 μg/mL of anti-Fas. Error bars represent mean ± standard deviation (SD). **P ≤ .01, ***P ≤ .001. IRF, interferon regulatory factor.