New insights into immune mechanisms of vitiligo.

Vitiligo is the most common depigmenting disorder, affecting 0.5% of the population. This stigmatizing disease has a major social impact with high unmet needs, and no real curative intervention has been reported so far. Vitiligo is characterized by the development of white macules resulting from a loss of epidermal melanocytes, which can result from cell destruction through melanocyte-specific cytotoxic immune response and melanocyte detachment through a defective adhesion system. Multiple mechanisms have been suggested to be involved in melanocyte disappearance: genetic predisposition, environmental triggers, metabolic abnormalities, altered inflammatory and immune responses. The autoimmune and inflammatory theory is the leading hypothesis. Indeed, vitiligo is often associated with autoimmune diseases; genome-wide association studies and functional pathway analyses have shown that most vitiligo susceptibility loci encode components of the immune system; and immune cells are found in the perilesional margin of actively depigmenting skin of vitiligo patients. However, studies support melanocytes intrinsic abnormalities in vitiligo associated with increased melanocytes stress leading to the release of dangers signals important for the activation of the immune system. This review aimed to overview the link between cellular stress, melanocyte function, and the abnormal inflammatory immune response in vitiligo. The involvement of innate and adaptive immune cells in the pathomechanisms leading to melanocyte loss observed in vitiligo will be discussed.