Autoimmune destruction of skin melanocytes by perilesional T cells from vitiligo patients

In vitiligo, cytotoxic T cells infiltrating the perilesional margin are suspected to be involved in the pathogenesis of the disease. However, it remains to be elucidated whether these T cells are a cause or a consequence of the depigmentation process. T cells we obtained from perilesional skin biopsies, were significantly enriched for melanocyte antigen recognition, compared with healthy skin-infiltrating T cells, and were reactive to melanocyte antigen-specific stimulation. Using a skin explant model, we were able to dissect the in situ activities of perilesional T cells in the effector phase of depigmentation. We show that these T cells could infiltrate autologous normally pigmented skin explants and efficiently kill melanocytes within this microenvironment. Interestingly, melanocyte apoptosis was accompanied by suprabasal keratinocyte apoptosis. Perilesional T cells did, however, not induce apoptosis in lesional skin, which is devoid of melanocytes, indicating the melanocyte-specific cytotoxic activity of these cells. Melanocyte killing correlated to local infiltration of perilesional T cells. Our data show that perilesional cytotoxic T cells eradicate pigment cells, the characteristic hallmark of vitiligo, thereby providing evidence of T cells being able to mediate targeted autoimmune tissue destruction.