Background and Aims Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor. AhR mediates mainly the effects of external molecules such as endocrine disruptors. It is clearly established that AhR activation induces a disequilibrium in T-cell maturation that participates to autoimmunity (Zhou et al 2016, Shinde et al. 2018). We aim to characterize the effects of AhR ligands on the homeostasis of thymic epithelial cells (TECs), cells that manage T cell differentiation and maturation in the thymus. Methods Primary human TECs were obtained from 7 different thymic biopsies and exposed for 24h to AhR exogenous ligands (TCDD and BAP) and an AhR endogenous ligand (FiCZ). Results AhR ligands deregulated the expression by TECs of key molecules involved in immune central tolerance process 1) the transcription factors (Aire, FezF2, and Prdm1) and 2) the tissue specific antigens (GAD67, PLP, Thyroglobulin...). More, AhR activation in TECs modulates the expression of cytokines (IL6, IL1β, TGFβ), and chemokines (CCL21, CXCL13), factors involved in T-cell differentiation and trafficking within the thymus. However, only TCDD stimulated TEC proliferation measured by CFSE cell labeling. TCDD also modulated TEC differentiation through epigenetic modifications (decreased CPG methylation) in keratin 5 (K5) gene promoter and concomitantly K5 gene expression. Conclusions Altogether, these results suggested that exposition to AhR ligands through their impact on TECs, may altered T-cell differentiation and maturation processes. Therefore, abnormal AhR activation would altered thymic functions and may favor autoimmune disease development.