CD8+ T cells from vitiligo perilesional margins induce autologous melanocyte apoptosis

Abstract

Cell-mediated autoimmunity has been suggested to be involved in the melanocyte apoptosis that occurs in vitiligo. We investigated the cytotoxicity to autologous melanocytes of CD8+ T cells from the perilesional margins and peripheral blood samples of vitiligo patients. CD8+ T cells isolated from skin biopsied from the edges of depigmented skin patches of vitiligo patients or from peripheral blood samples of the same donors were proliferated in culture medium. The primary cultures of CD8+ T cells and autologous melanocytes were mixed at ratios of 1:1, 1:2 or 1:5 and incubated for 3 days. The apoptosis of the melanocytes was analyzed by flow cytometry. Secreted cytokines in selected samples were measured by cytokine arrays. The results show that the CD8+ T cells were successfully isolated from the vitiligo perilesional margins. This cell population showed a significantly higher percentage of CD69 expression (56.13±3.55 versus 29.93±2.35%, p<0.01) and CD137 expression (41.74±1.06 versus 25.97±1.63%, p<0.01) compared with CD8+ T cells in peripheral blood from the same donors. The co-culturing of CD8+ T cells from lesional skin with autologous melanocytes induced apoptosis in the melanocytes (16.63±1.21, 16.71±0.63 and 18.32±1.60% for CD8+ T cells and autologous melanocytes at ratios of 1:1, 1:2 and 1:5, respectively). IL-6 levels were much higher in the co-culture (3.01-fold higher than in a melanocyte monoculture and 17.32-fold higher than in a CD8+ T-cell monoculture). The CD8+ T cells were also demonstrated to secrete more IL-13. Taken together, our data demonstrate that the infiltration of active CD8+ T cells takes place in the vitiligo perilesional margins. Those CD8+ T cells present significantly higher activation levels and higher cytotoxicity to autologous melanocytes than their counterparts from peripheral blood samples. These data suggest that CD8+ T cells are likely to be involved in the pathogenesis of vitiligo.

Regulatory T cells in vitiligo: Implications for pathogenesis and therapeutics

“…In addition, several studies have identified a pivotal role for cytotoxic T cells in inducing melanocyte-specific destruction in vitiligo [7], including the findings that CD8 + T cells isolated from vitiligo skin are cytotoxic to melanocytes, recognise melanocyte-specific autoantigens [7], and induce autologous melanocyte apoptosis through IL-6 and IL-13 [9] (Fig. 1).…”

IFN-γ Promotes Apoptosis of Melanocytes in Vitiligo

“…For instance, CD8+ T cell-mediated melanocyte destruction has been demonstrated in vitiligo. In addition, an increased accumulation of CD8+ T cells in peripheral blood mononuclear cells (PBMCs) and perilesional skin of patients with progressive vitiligo has been reported (1,3). On the other hand, elevated expression of Th1 cell specific transcription factor (T-bet) and cytokine (IFN-γ) was indicated in PBMCs of patients with vitiligo (2).…”

“…Cytotoxicity via induction of apoptosis has been considered as a major effector mechanism of autoreactive CTLs. Therefore, recruited CD8+ T cells may specifically induce autologous melanocyte apoptosis resulting in disappearance of melanocytes (3). On the other hand, CD4+ Th1 cells (one of the main sources of IFN-γ production) are required for optimal induction of antigen-specific CD8+ T cell effector responses.…”

A New View of Vitiligo: Looking at Normal-Appearing Skin

“…Still, plasmacytoid dendritic cells, which are part of the perilesional cellular infiltrate and the major IFN-α-producing cell subset, may sustain the recruitment and activation of T cells (Bertolotti et al, 2014). In support of this mechanism, apoptosis in vitiligo melanocytes has also been demonstrated (Wu et al, 2013).…”