Exploring the hair follicle immune privilege state in nonsegmental vitiligo

Background The pathogenesis of nonsegmental vitiligo (NSV) and alopecia areata (AA) overlap in several aspects. In AA, the anagen hair follicle (HF) undergoes a collapse of immune privilege (IP). No previous studies assessed the IP of the HF in NSV. Objective To assess the IP in NSV compared with AA. Patients and methods Twenty NSV with scalp lesions and 20 scalp AA patients were included in this prospective comparative study. Clinical assessment and immunohistochemical examination of punch biopsies from lesional and nonlesional scalp were done for interferon gamma (IFN-γ), transforming growth factor beta 1 (TGF-β1), major histocompatibility complex (MHC)I, and MHCII in the HF and epidermis. Results In AA, there was upregulation of IFN-γ and MHCI and downregulation of TGF-β1 denoting impaired IP in lesional compared with nonlesional HF. In NSV, no difference in IFN-γ was found between lesional and nonlesional HF. MHCI and MHCII were upregulated in lesional HF, while TGF-β1 was significantly lower in lesional HF. A significantly higher expression of IFN-γ and MHCI was detected in lesional epidermis compared with lesional HF in NSV patients. Lesional HF in AA showed significantly higher expression of IFN-γ and MHCI and significantly lower expression of TGF-β1 than lesional HF in NSV, denoting preserved IP in NSV. Conclusion IP is preserved in HF in NSV compared with AA, protecting the follicular melanocytes from autoimmune attacks.