Pathophysiology Of Vitiligo Research Articles

Serum vitamins and trace elements in vitiligo patients: A systematic review and meta‐analysis of observational studies

AbstractVitiligo is one of the most common pigmentary skin disorders, which significantly impacts the quality of life. The aetiology and pathophysiology of vitiligo are still unclear, but one of the proposed mechanisms is oxidative damage interrupting melanogenesis. The purpose of this study was to demonstrate the serum levels of trace elements and vitamins and to systematically review the evidence comparing vitiligo patients with a healthy group. We comprehensively retrieved all studies related to vitiligo and the serum levels of vitamins and minerals from databases such as PubMed, EMBASE, Scopus, Web of Science, Magiran, SID and ISC up to December 2022. Quality assessment and data extraction were conducted by two independent reviewers. Pooled standard mean differences with 95% confidence intervals were estimated using random‐effects models. Our meta‐analysis revealed no significant differences in serum levels of Vitamin B12 and copper. It was concluded that serum concentrations of Vitamin D, Vitamin E, and zinc were lower in vitiligo patients. Conversely, these patients exhibited higher levels of selenium and folic acid compared with healthy individuals. These results might affect the potential use of vitamin and mineral supplementation in vitiligo treatment.

Aetiopathogenesis of Vitiligo.

Vitiligo is a chronic auto-immune disease characterized by skin depigmentation due to the loss of melanocytes. The better understanding of the disease mechanisms is currently undergoing a significant dynamism, opening a new era in therapeutic development. The pathophysiology of vitiligo has attracted the attention of researchers for years and many advances have been made in clarifying the crosstalk between the cellular players involved in the development of vitiligo lesions. The understanding of the complex interactions between epidermal cells (i.e. melanocytes and keratinocytes), dermal fibroblasts, and immune cells, led to a better characterization of the signals leading to the loss of melanocytes. Recent advances highlighted the role resident T memory cells in the development and recurrence of lesions. This narrative review aims to give an overview of the mechanisms leading to melanocyte disappearance in vitiligo, with a focus on the intercellular interaction network involved in the activation of the local skin immune response.

Serum Copper and Zinc Levels Among Iranian Vitiligo Patients.

Vitiligo is a chronic skin disease, which its etiopathogenesis is not fully understood. Numerous studies have suggested that oxidative stress may play a role in the pathophysiology of vitiligo. There are controversial reports as to the changes of serum trace elements, copper (Cu) and zinc (Zn) levels in vitiligo patients. We evaluated the alterations in the level of serum Cu and Zn among a group of Iranian vitiligo patients. The levels of serum Cu and Zn were compared between 117 vitiligo patients and 137 healthy controls using atomic absorption spectrophotometry. The mean Cu and Zn levels in the cases (113.57 ± 59.43 and 95.01 ± 58.95 μg/dl, respectively) were significantly lower than those of the controls (138.90 ± 38.14 and 121.83 ± 33.80 μg/dl, respectively) (P = 0.00). We also observed significantly lower serum Cu and Zn concentrations in young (< 50 years) than the elderly (≥ 50 years) patients (P = 0.00). The mean Cu and Zn levels in the patients with generalized vitiligo (111.63±54.18 and 93.11±59.33 μg/dl, respectively) were significantly lower than patients with localized vitiligo (120.74 ±71.64 and 98.69±58.63 μg/dl, respectively) and those in the control (P = 0.00). The serum Cu/Zn ratio obtained in the young and male patients was higher than those in their matched controls (P = 0.01). The current study has shown that the disturbance of serum Cu and Zn levels is associated with vitiligo, and may play an important role in the disease development of Iranian patients.

Vitiligo as a potential degenerative disease: from oxidative stress to cellular senescence

Vitiligo is a depigmentation disorder characterized by the loss of melanocytes in the skin, which is aggravated by oxidative stress. The relationship between oxidative stress and cellular senescence is still unclear despite considerable research on melanocyte senescence in vitiligo in recent years. Many chronic diseases associated with oxidative stress, that is, degenerative diseases, have been shown to ultimately result in cellular senescence due to sustained activation of reactive oxygen species. This study advances research on the pathophysiology of vitiligo and its treatment options by summarizing the role of oxidative stress and melanocyte senescence in vitiligo and investigating the mechanisms behind the interaction of melanocyte senescence with oxidative stress. Keywords: Vitiligo, melanocytes, oxidative stress, cellular senescence, age

Identification of the Role of Wnt/β-Catenin Pathway Through Integrated Analyses and in vivo Experiments in Vitiligo.

PurposeVitiligo is an acquired depigmentation skin disease, which affects an average of 1% of the world’s population. The purpose of this study is to identify the key genes and pathways responsible for vitiligo and find new therapeutic targets.MethodsThe datasets GSE65127, GSE53146, and GSE75819 were downloaded from the Gene Expression Omnibus (GEO) database. R language was used to identify the differentially expressed genes (DEGs) between lesional skin of vitiligo and non-lesional skin. Next, the key pathways were obtained by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The protein–protein interaction (PPI) networks were conducted by STRING database and Cytoscape software. Subsequently, module analysis was performed by Cytoscape. Among these results, the Wnt/β-catenin pathway and melanogenesis pathway caught our attention. The expression level of β-catenin, microphthalmia-associated transcription factor (MITF) and tyrosinase (TYR) was detected by immunofluorescence in vitiligo lesions and healthy skin. Moreover, zebrafish was treated with XAV-939, an inhibitor of the Wnt/β-catenin pathway. After that, the area of melanin granules as a percentage of the head area was measured. The mRNA expression of β-catenin, lymphoid-enhancing factor 1(lef1), tyr and mitf were detected by q-PCR (quantitative polymerase chain reaction) in zebrafish (Danio rerio).ResultsA total of 2442 DEGs were identified, including 1068 upregulated and 1374 downregulated DEGs. The key pathways were identified by GO and KEGG analyses, such as “NOD-like receptor signaling pathway”, “Wnt signaling pathway”, “Melanogenesis”, “mTOR signaling pathway”, “PI3K-Akt signaling pathway”, “Calcium signaling pathway” and “Rap1 signaling pathway”. The immunofluorescence results showed that the level of β-catenin, MITF and TYR was significantly downregulated in vitiligo lesional skin. In zebrafish, the mean percentage area of melanin granules and the expression of β-catenin, lef1, tyr and mitf were decreased after treated with XAV-939.ConclusionThe present study identified key genes and signaling pathways associated with the pathophysiology of vitiligo. Among them, the Wnt/β-catenin pathway played an essential role in pigmentation and could be a breakthrough point in vitiligo treatment.

Skin ‑ a vast organ with immunological function (Review)

The skin is an organ with multiple functions, where important inflammatory and immunological processes take place. The integrity of the skin barrier is necessary for it to fulfill its roles. An intact skin barrier requires a physiological keratinization process, but also a normal cutaneous microbial flora. Any change in the proliferation and differentiation of keratinocytes entails the disruption of the skin barrier and the triggering of inflammatory and immunological processes at this level, in response to the aggression of external pathogens. Also, there are several specialised immune cells in the skin (Langerhans cells, T regulator cells, T helper cells), that maintain a balance between pro-inflammatory and anti-inflammatory processes at this level. Disturbing the immune homeostasis causes inflammation and allergic skin reaction. Psoriasis and atopic dermatitis are two inflammatory diseases of the skin, characterized by perturbation of the mechanisms of skin barrier formation. The immune system of the skin is also involved in the pathophysiology of vitiligo and pemphigus. The aim of this review is to offer a brief presentation of the inflammatory and immunological processes that occur in the skin.

Role of Anti-oxidants in the Treatment of Vitiligo

Introduction: The role of free radicals and oxidative damage in the pathophysiology of vitiligo has been documented in recent studies. Antioxidant supplementation has been reported to be useful in the treatment of vitiligo.&#x0D; Objective: To evaluate the role of oral antioxidants supplementation therapy in the treatment of vitiligo by assessing the onset of repigmentation and oxidative stress.&#x0D; Materials and Methods: A total of 80 cases of vitiligo randomized into two groups: antioxidant and placebo comprising 40 patients each and were followed up for 8 weeks for the assessment of onset of repigmentation of vitiliginous lesions as primary outcome. The activities of Malondialdehyde (MDA), Vitamin C, and Vitamin E in serum and of Catalase (CAT) in erythrocytes of patients at baseline and at end of eight weeks were also assessed by using the spectrophotometric assay.&#x0D; Results: The onset of repigmentation was noted significantly earlier among the anti-oxidant group as compared to the placebo group (p=0.015). At the baseline, between the two groups, no significant difference was found in the different biochemical parameters. However, at the end of 2 months the level of MDA (p&lt;0.001) was found to be significantly lower and that of Vitamin E (p&lt;0.001) and CAT (p=0.005) was significantly higher among the anti-oxidants group as compared to the placebo group.&#x0D; Conclusion: Antioxidant supplementation carried a better response in terms of early onset of repigmentation and significant decrease in the oxidative stress, in the short follow up of two months.

Biomarkers of disease activity in vitiligo: A systematic review.

The pathophysiology of vitiligo is complex although recent research has discovered several markers which are linked to vitiligo and associated with disease activity. Besides providing insights into the driving mechanisms of vitiligo, these findings could reveal potential biomarkers. Activity markers can be used to monitor disease activity in clinical trials and may also be useful in daily practice. The aim of this systematic review was to document which factors have been associated with vitiligo activity in skin and blood. A second goal was to determine how well these factors are validated in terms of sensitivity and specificity as biomarkers to determine vitiligo activity. Both in skin (n=43) as in blood (n=66) an adequate number of studies fulfilled the predefined inclusion criteria. These studies used diverse methods and investigated a broad range of plausible biomarkers. Unfortunately, sensitivity and specificity analyses were scarce. In skin, simple histopathology with or without supplemental CD4 and CD8 stainings can still be considered as the gold standard, although more recently chemokine (C-X-C motif) ligand (CXCL) 9 and NLRP1 have demonstrated a good and possibly even better association with progressive disease. Regarding circulating biomarkers, cytokines (IL-1β, IL-17, IFN-γ, TGF-β), autoantibodies, oxidative stress markers, immune cells (Tregs), soluble CDs (sCD25, sCD27) and chemokines (CXCL9, CXCL10) are still competing. However, the two latter may be preferable as both chemokines and soluble CDs are easy to measure and the available studies display promising results. A large multicenter study could make more definitive statements regarding their sensitivity and specificity.

Vitiligo: An Update on Pathophysiology and Treatment Options.

The pathophysiology of vitiligo is becoming increasingly clarified. In non-segmental vitiligo, early factors include activation of innate immunity, inflammasome activation, oxidative stress, and loss of melanocyte adhesion. Nonetheless, the main mechanism leading to non-segmental vitiligo involves an immune-mediated destruction of melanocytes. Anti-melanocyte-specific cytotoxic T cells exert a central role in the final effector stage. Genetic research revealed a multi-genetic inheritance displaying an overlap with other autoimmune disorders. However, some melanocyte-specific genes were also affected. Segmental vitiligo carries a different pathogenesis with most evidence indicating a mosaic skin disorder. Current management includes topical corticosteroids and immunomodulators. Narrow-band ultraviolet B can be used in patients not responding to topical treatment or in patients with extensive disease. Pigment cell transplantation offers an alternative for the treatment of segmental vitiligo or stable non-segmental lesions. Recent findings have revealed new targets for treatment that could lead to more efficient therapies. Targeted immunotherapy may halt the active immune pathways, although combination therapy may still be required to induce satisfying repigmentation. A recently established core set of outcome measures, new measurement instruments, and biomarker research pave the way for future standardized clinical trials.

Targeting CTLA-4, PD-L1 and IDO to modulate immune responses in vitiligo.

For decades, an extensive debate is continued on the pathophysiology of vitiligo. Numerous hypotheses have been put forward, and many supported by well-documented arguments. Regardless of the initiating steps, most experts agree that an immune-based melanocyte destruction is responsible for the final steps leading to epidermal depigmentation. It is remarkable that currently the only therapeutic approach to counter this phenomenon consists of non-specific local and systemic immunosuppressants. Immunotherapy for melanoma reveals that targeting factors involved in peripheral tolerance are sufficient to break the natural defense mechanisms to develop skin depigmentations. Therapeutically enhancing these immune checkpoints seems therefore a promising long-term therapy for vitiligo. In this viewpoint, we propose this strategy as a promising therapeutic option for vitiligo. Several approaches are proposed with a focus on cytotoxic T-lymphocyte-associated protein 4, programmed death ligand-1 and indoleamine 2,3-dioxygenase.

Comparison of oxidant-antioxidant status in patients with vitiligo and healthy population.

Vitiligo is a well-recognized pigmentary disorder of the skin and /or mucous membrane characterized by circumscribed ivory or chalky white macules devoid of identifiable melanocytes. The pathogenesis of vitiligo is complex and still not well understood. According to autocytotoxic hypothesis, oxidative stress has been suggested to be the initial pathogenic event in melanocyte degeneration. The role of free radicals and oxidative damage in the pathophysiology of vitiligo has been documented in recent studies. To evaluate the role of oxidative stress in patients with vitiligo and of healthy controls by measuring levels of the oxidant malondialdehyde (MDA) and antioxidants vitamin C and vitamin E in serum and catalase (CAT) in erythrocytes. A total of 80 clinically diagnosed cases of vitiligo and 80 control subjects were included in the study to assess the activity of MDA, vitamin C and vitamin E in serum and CAT in erythrocytes of patients and controls by using the spectrophotometric assay. There was statistically significant increase in the levels of MDA in patients with vitiligo compared to the control group (p<0.001). No significant difference was found in the levels of vitamin C (p=0.411) and vitamin E (p=0.771) between the patients with vitiligo and control group. The levels of CAT in the vitiligo patients were found to be significantly lower than those of controls (p<0.001). Increased oxidative stress and decreased catalase have been observed in vitiligo patients and the data suggesting that the free radicals may be involved in the destruction of melanocytes or dysregulation of melanogenesis.

The association of FOXO3A gene polymorphisms with serum FOXO3A levels and oxidative stress markers in vitiligo patients

Vitiligo is an acquired epidermal pigment loss of the skin. Oxidative stress is one of the major theories in the pathophysiology of vitiligo. FOXO3A is the forkhead members of the class O (FOXO) transcription factors, and plays an important role in cell cycle regulation, apoptosis, oxidative stress, and DNA repair. The aim of our study was to investigate FOXO3A gene polymorphisms and FOXO3A protein levels, activities of superoxide dismutase (SOD) and catalase antioxidant enzymes in vitiligo patients and healthy controls. Moreover, the level of plasma advanced oxidation protein products (AOPP) in subjects was evaluated to understand the possible role of protein oxidation in disease etiology. Study groups included 82 vitiligo patients and 81 unrelated healthy controls. FOXO3A polymorphisms were determined using polymerase chain reaction–restriction fragment length polymorphism method. FOXO3A levels and catalase activity were measured by ELISA whereas AOPP levels and SOD activity was measured by spectrophotometric analysis. We found a significant relationship between rs4946936 polymorphism of FOXO3A gene and vitiligo/active vitiligo patients (p=0.017; p=0.019 respectively), but not for rs2253310 (p>0.05). SOD activity and AOPP levels of vitiligo patient were increased compared with control group, whereas FOXO3A levels and catalase enzyme activity of vitiligo patient were decreased compared with control group (p<0.05). Our study indicates that rs4946936 of FOXO3A gene may associate susceptibility of vitiligo, especially active vitiligo. Moreover, our results confirm that oxidative stress may play a role in the pathophysiology of vitiligo. Further studies with larger samples are required to elucidate the role of FOXO3A in vitiligo.

The association of Foxo3a gene polymorphisms with serum Foxo3a levels and oxidative stress markers in vitiligo patients

Vitiligo is an acquired epidermal pigment loss the skin with destruction of melanocytes. Oxidative stress is one of the major theories in the pathophysiology of vitiligo. FOXO3a is the forkhead members of the class O (FOXO) transcription factors, and plays important role in cell cycle regulation, apoptosis, oxidative stress, and DNA repair. The aim of our study was to investigate, for the first time, FOXO3a gene polymorphisms and FOXO3a protein levels, activities of superoxide dismutase (SOD) and catalase antioxidant enzymes in vitiligo patient and healthy controls. Moreover, plasma advanced oxidation protein products (AOPP) levels in subjects was evaluated to understand the possible role of protein oxidation in disease etiology. Studies groups included 82 vitiligo patients and 81 unrelated healthy controls. FOXO3a polymorphisms were determined using polymerase chain reaction-restriction fragment length polymorphism method. FOXO3a levels and catalase activity were measured by ELISA whereas AOPP levels and SOD activity were measured spectrophotometric analyses. We found a significant relationship between rs4946936 polymorphism of FOXO3a gene and vitiligo/active vitiligo patients (p=0.017; p=0.019 respectively), but not for rs2253310 (p>0.05). SOD activity and AOPP levels of vitiligo patient were increased compared with control group, whereas FOXO3a levels and catalase enzyme activity of vitiligo patient were decreased compared with control group (p<0.05). Our study indicates that rs4946936 of FOXO3a gene may associate susceptibility of vitiligo, especially active vitiligo. Moreover, our results confirm that oxidative stress may play a role in the pathophysiology of vitiligo. Further studies with larger samples are required to elucidate the role of FOXO3a in vitiligo.

Association study between nonsense polymorphism (rs2039381, Gln71Stop) of Interferon-ε and susceptibility to vitiligo in Korean population

Interferons (IFNs) are related to autoimmune responses. IFN-epsilon (IFNE) is included in IFN family, and may modulate immunological functions. Inflammation modulating functions of IFNE may be related with the pathophysiology of vitiligo. To investigate the association of nonsense polymorphism (rs2039381, Gln71Stop) of interferon-ε (IFNE) and susceptibility to vitiligo, we conducted a case-control association study in 265 non-segmental vitiligo (NSV) patients and 320 healthy controls. The nonsense single nucleotide polymorphism (SNP) (rs2039381, Gln71Stop) of IFNE was genotyped by direct sequencing. Multiple logistic regression models (log-additive, dominant, and recessive models) were applied to determine odds ratios (OR), 95% confidence interval (CI), and p values. The rs2039381 (Gln71Stop) of IFNE did not show significant differences between NSV patient group and control group. However, we found that in childhood onset NSV groups, the IFNE nonsense polymorphism (rs2039381, Gln71Stop) showed a significant association. There was significantly different distribution of nonsense polymorphism of rs2039381 (Gln71Stop) of IFNE between NSV patients (childhood <18 years) and control subjects. This study suggests that rs2039381 (Gln71Stop) polymorphism of IFNE may be related to onset time of vitiligo in NSV patients.

The polymorphism of catalase T/C codon 389 in exon 9 and vitiligo susceptibility: a meta‐analysis

The exact aetiology of vitiligo has not yet been established. Oxidative stress is involved in the pathophysiology of vitiligo. It has been described that some polymorphisms in the catalase (CAT) gene may affect the risk of vitiligo. However, the results were inconsistent. We performed a meta-analysis of the published studies to derive a more precise estimate of the association between CAT T/C at codon 389 in exon 9 polymorphisms and vitiligo risk. The PubMed, Medline, Cochrane Library, China National Knowledge Infrastructure (CNKI) databases were searched to identify relevant published studies. Four case-control studies (cases, 645; controls, 689) that investigated the association between C/T polymorphisms of CAT exon 9 and the risk of vitiligo were retrieved and analysed. Our findings suggested a significant association between the CAT T/C exon 9 polymorphism and vitiligo risk (CT + TT vs. CC pooled odds ratio, 1.43; 95% confidence interval, 1.14-1.80; P = 0 .002). We found a significant correlation between the CAT T/C exon 9 polymorphism and the risk of vitiligo.

Study of Oxidative Stress in Vitiligo

Vitiligo is an idiopathic, acquired, circumscribed, hypomelanotic skin disorder, characterized by milky white patches of different sizes and shapes. It is due to the destruction of melanocytes resulting in the absence of pigment production of the skin and mucosal surfaces. Oxidative stress has been implicated in pathophysiology of vitiligo. To study the activity of blood Superoxide dismutase (SOD) and Glutathione peroxidase (GPx) in vitiligo patients. A case-control study was conducted in which 100 patients were enrolled after written consent. 50 cases were of active vitiligo and 50 served as control (25 healthy control and 25 with stable vitiligo). SOD-In our study, among the active vitiligo cases 90% had high level of SOD and 10% had normal level of SOD. Among the stable vitiligo controls, 92% had normal level of SOD and 8% had low levels of SOD.The difference between active vitiligo cases and stable vitiligo control as well as with healthy control was statistically significant (P value<0.05). GPx-Among the active vitiligo cases 74% had normal GPx levels, 22% had low and only 4% had high levels of GPx. Among the stable vitiligo controls, 64% had normal GPx levels, 16% had low, and 20% had high levels of GPx. The difference between active vitiligo cases and stable vitiligo control as well as with healthy control was statistically not significant (P value>0.05). Our study shows that oxidative stress is involved in the pathophysiology of vitiligo, as indicated by the high levels of serum superoxide dismutase activity.

Circulatory levels of antioxidants and lipid peroxidation in Indian patients with generalized and localized vitiligo

Vitiligo is an acquired skin disease, characterized by white areas on the skin due to loss of functional melanocytes. The pathogenesis of the disease is still unclear. Published data show the involvement of oxidative stress in the pathophysiology of vitiligo. A total of 30 vitiligo patients and 30 healthy controls were included in this study. We estimated serum levels of malondialdehyde (MDA), vitamins E and C, total antioxidant activity and whole blood levels of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in vitiligo patients and controls. We found significantly higher levels of MDA and significantly lower levels of SOD, GPx, vitamins C and E and total antioxidant activity in vitiligo patients compared with controls. This study is a maiden attempt to report on antioxidant parameters of both generalized/localized-type Indian vitiligo patients. Our results confirmed that oxidative stress may play an important role in the pathogenesis of vitiligo and cause melanocyte damage in vitiligo.

Topical calcipotriol as monotherapy and in combination with psoralen plus ultraviolet A in the treatment of vitiligo

Background Recent advances in the pathophysiology of vitiligo have demonstrated defective calcium homeostasis in depigmented skin. 1,25-Dihydroxyvitamin D3 may be involved in the regulation of melanin synthesis, and receptors for 1,25-dihydroxyvitamin D3 have been demonstrated on melanocytes. Objectives We conducted an open study to determine the efficacy and tolerability of calcipotriol cream as monotherapy and in conjunction with psoralen plus ultraviolet A (PUVA) in the treatment of vitiligo. Methods Twenty-six patients with vitiligo affecting 5–40% of their skin were recruited. Twenty-two were treated with twice-daily topical calcipotriol monotherapy (50 µg g−1) and four were placed on combination treatment with twice-daily topical calcipotriol 50 µg g−1 in conjunction with topical or oral 8-methoxypsoralen PUVA three times weekly. Results Treatment was well tolerated at all sites and no adverse effects were reported. After a therapy time of 3–9 months (mean 6 months), 77% (17 of 22) of those treated with monotherapy showed 30–100% improvement, and three of the four patients on combination treatment showed good response. Conclusions Topical calcipotriol appears to be an effective and well-tolerated treatment for vitiligo and can be safely used in conjunction with PUVA, but controlled studies are necessary to exclude the possibility of spontaneous repigmentation.

A comparative study of superoxide dismutase, catalase, and glutathione peroxidase activities and nitrate levels in vitiligo patients

Several groups have shown the involvement of oxidative stress in the pathophysiology of vitiligo. In this study, we examined the erythrocyte and plasma activities of glutathione peroxidase and Cu/Zn superoxide dismutase, plasma nitrite/nitrate levels, and erythrocyte catalase activity in 23 vitiligo patients and 25 controls. The results show that erythrocyte superoxide dismutase activity and plasma nitrite/nitrate levels are high in vitiligo patients. Our study confirms that oxidative stress is involved in the pathophysiology of vitiligo, as indicated by the high levels of erythrocyte superoxide dismutase activity and plasma nitrite/nitrate.

Peripheral CD8+ T Cell Tolerance Against Melanocytic Self-Antigens in the Skin Is Regulated in Two Steps by CD4+ T Cells and Local Inflammation: Implications for the Pathophysiology of Vitiligo

Experimental evidence has suggested a role for CD8+ cytotoxic T lymphocytes (CTL) in the pathophysiology of vitiligo, a pigmentation disorder with focal loss of melanocytes in the skin. The discovery of tyrosinase-related protein 2 (TRP2) as a model melanocytic self-antigen recognized by CD8+ CTL in C57BL/6 mice allowed us to analyze the requirements for CD8+ T cell-mediated autoimmune destruction of melanocytes in an experimental model. Using two different genetic methods for the induction of cellular immunity in vivo, gene gun bombardment of the skin and injection of recombinant adenovirus, we show that peripheral tolerance of CD8+ T cells recognizing a single TRP2-derived H2-Kb-binding peptide is regulated in two steps. In the induction phase, stimulation and expansion of TRP2-specific CD8+ T cells in vivo depend on CD4+ T cell help. In the effector phase, autoimmune destruction of melanocytes in the skin depends on local inflammation. Our results suggest that accidental stimulation of CD8+ CTL recognizing major histocompatibility complex class I-binding peptides derived from melanocytic proteins in the context of an inflammatory skin disease may play an important role in the pathophysiology of vitiligo.