4-Tertiary butyl phenol exposure sensitizes human melanocytes to dendritic cell-mediated killing: relevance to vitiligo.

The trigger initiating an autoimmune response against melanocytes in vitiligo remains unclear. Patients frequently experience stress to the skin prior to depigmentation. 4-tertiary butyl phenol (4-TBP) was used as a model compound to study the effects of stress on melanocytes. Heat shock protein (HSP)70 generated and secreted in response to 4-TBP was quantified. The protective potential of stress proteins generated following 4-TBP exposure was examined. It was studied whether HSP70 favors dendritic cell (DC) effector functions as well. Melanocytes were more sensitive to 4-TBP than fibroblasts, and HSP70 generated in response to 4-TBP exposure was partially released into the medium by immortalized vitiligo melanocyte cell line PIG3V. Stress protein HSP70 in turn induced membrane tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression and activation of DC effector functions towards stressed melanocytes. Melanocytes exposed to 4-TBP demonstrated elevated TRAIL death receptor expression. DC effector functions were partially inhibited by blocking antibodies to TRAIL. TRAIL expression and infiltration by CD11c+ cells was abundant in perilesional vitiligo skin. Stressed melanocytes may mediate DC activation through release of HSP70, and DC effector functions appear to play a previously unappreciated role in progressive vitiligo.