Calcitonin Gene-Related Peptide (CGRP) May Award Relative Protection from Interferon-γ-Induced Collapse of Human Hair Follicle Immune Privilege

This pilot study explored the role of calcitonin gene-related peptide (CGRP) in protecting human hair follicles (HFs) from immune privilege (IP) collapse induced by interferon-gamma (IFNγ), a process relevant to alopecia areata (AA). The study found that CGRP, when administered before IFNγ, significantly reduced the overexpression of major histocompatibility complex (MHC) class I and II, suggesting its potential as an 'IP guardian.' However, CGRP could not restore IP once it had collapsed. These findings indicated that CGRP might prevent AA progression by downregulating MHC I/β2mg, thus suppressing autoantigen presentation to CD8+ T cells. The study also noted that reduced CGRP levels in AA patients might reflect a deficiency in its immunoinhibitory function. The research suggested that CGRP's protective mechanism might involve the suppression of nitric oxide production, similar to its action in ocular IP. The study was supported by grants from the National Alopecia Areata Foundation and the Deutsche Forschungsgemeinschaft.