IL-15/IL-15Rα Signaling Is a Guardian of Human Hair Follicle Immune Privilege and Promotes Hair Growth

The study investigates the role of IL-15/IL-15Rα signaling in maintaining human hair follicle immune privilege (HF-IP) and promoting hair growth. It was found that IL-15 protects against HF-IP collapse, restores HF-IP, and delays catagen development in human hair follicles. Conversely, silencing IL-15Rα leads to premature catagen, reduced hair matrix proliferation, and weakened HF-IP. Additionally, AA patients exhibit reduced IL-15Rα and common γ-chain expression, indicating decreased sensitivity to IL-15 signaling. The findings suggest that stimulating IL-15Rα signaling could promote hair growth and prevent rapid AA relapse after stopping JAKi therapy.