The Smyth line (SL) of chicken is an excellent animal model for human autoimmune vitiligo. In SL vitiligo (SLV) post-natal loss of melanocytes in feathers appears to be due to cell-mediated immunity. In this study, leukocyte-infiltration and associated expression (RNA) of immune function-related cytokines in growing feathers were investigated throughout SLV-development and -progression. Both leukocyte infiltration and cytokine expression levels started to increase near visible SLV onset (early SLV), reached peak levels during active SLV, and decreased to near pre-vitiligo levels after complete loss of melanocytes. Specifically, significant increases were noticed in relative proportions of T cells, B cells, and MHC II-expressing cells during active SLV. Levels of T cell infiltration were higher than those of B cells, with more CD8+ than CD4+ cells throughout SLV. Elevated leukocyte infiltration in early and active SLV was accompanied by increased levels of cytokine expression, especially in interferon-gamma, interleukin (IL)-10 and IL-21. Low expression of IL-4 and IL-17 did not suggest important roles of Th2 and Th17 cells in SLV pathogenesis. Taken together, SLV appears to be a Th1 polarized autoimmune disease, whereby interferon-gamma expression is strongly associated with parallel increases in IL-10 and IL-21, particularly during early and active stages of SLV.
Autoimmune diseases in human patients only become clinically manifest when the disease process has developed to a stage where functional compensation by the afflicted organ or system is not possible any more. In order to understand the initial etiologic and pathogenic events that are generally not yet accessible in humans, appropriate animal models are required. In this respect, spontaneously developing models - albeit rare – reflect the situation in humans much more closely than experimentally induced models, including knockout and transgenic mice. The present review describes three spontaneous chicken models for human autoimmune diseases, the Obese strain (OS) with a Hashimoto-like autoimmune thyroiditis, the University of California at Davis lines 200 and 206 (UCD-200 and 206) with a scleroderma-like disease and the amelanotic Smyth line with a vitiligo-like syndrome (SLV). Special emphasis is given to the new opportunities to unravel the genetic basis of these diseases in view of the recently completed sequencing of the chicken genome.
Vitiligo is one of the most common pigmentary skin disorders; it is characterized by circumscribed depigmented macules due to the destruction of melanocytes. Although the etiology of vitiligo has not been fully elucidated, multiple factors including autoimmune and oxidative stress have been implicated in the pathogenesis of vitiligo. In contrast, dermal melanocytosis is histologically characterized by the presence of dermal melanocytes. It has been described that there are ectopic dermal melanocytes, which have failed to reach their proper location. A literature search revealed very few reports of patients with vitiligo developing vitiligo within dermal melanocytosis. Here, we report two cases of patients with vitiligo that occurred at pre-existing sites of dermal pigmented lesions. The histopathology showed the loss of epidermal melanocytes in spite of the existence of melanocytes in the dermis. There was no significant infiltration of inflammatory cells in the dermis. These cases illustrate unknown environmental factors as well as heterogeneity.
Dermal melanocytosis; Vitiligo
Vitiligo is a common depigmenting disorder resulting from the loss of melanocytes in the skin. The pathogenesis of the disease remains obscure, although autoimmune mechanisms are thought to be involved. Indeed, autoantibodies and autoreactive T lymphocytes that target melanocytes have been reported in some vitiligo patients. The objective of this study was to identify pigment cell antigens that are recognized by autoantibodies in vitiligo. Using IgG from vitiligo patients to screen a melanocyte cDNA phage-display library, we identified the melanin-concentrating hormone receptor 1 (MCHR1) as a novel autoantigen related to this disorder. Immunoreactivity against the receptor was demonstrated in vitiligo patient sera by using radiobinding assays. Among sera from healthy controls and from patients with autoimmune disease, none exhibited immunoreactivity to MCHR1, indicating a high disease specificity for Ab’s against the receptor. Inhibition of MCH binding to its receptor by IgG from vitiligo patients was also shown.
Vitiligo is a relatively common progressive depigmentary condition that is believed to be due to the autoimmune-mediated loss of epidermal melanocytes. High frequencies of self-reactive T lymphocytes directed toward melanocyte differentiation antigens are found in vitiligo patients and might be directly responsible for the pathogenesis of the disease. An interesting aspect of vitiligo is its relation to melanoma: cytotoxic T lymphocytes directed to self antigens shared by normal melanocytes and melanoma cells are found in both conditions, but the resulting immune reactions are completely different. From this standpoint, the selective destruction of pigment cells that occurs in cases of vitiligo is the therapeutic goal sought in melanoma research.
Presentation of the hypothesis
Our working hypothesis is that vitiligo patients might represent a unique source of therapeutic cells to be used in allo-transfer for HLA-matched melanoma patients. The adoptive transfer of ex-vivo generated autologous tumor-specific T cells is a therapy that has met with only limited success, essentially because of inability to isolate therapeutically valuable T cells from the majority of tumor patients. Ideally, model systems where strong and efficient responses against the same (tumor) antigens are achieved would represent a better source of therapeutic cells. We believe it is possible to identify one such model in the melanoma-vitiligo dichotomy: T lymphocytes specific for different melanocyte differentiation antigens are found in vitiligo and represent the effective anti-melanocyte reactivity that is often ineffective in melanoma.
Testing the hypothesis
Melanocyte-specific T cell clones can be isolated from the peripheral blood of vitiligo patients and tested for their capacity to efficiently expand in vitro without loosing their cytotoxic activity and to migrate to the skin. Cytotoxicity against melanoma patients' non-tumor cells can also be tested. In addition, it would be interesting to attempt an in vivo animal model. If the results obtained from these validation steps will be satisfactory, it might be possible to plan the clinical grade preparation of relevant clones for transfer.
Implications of the hypothesis
When translated into a clinical trial, the possibility of in vitro selecting few effective tumor-specific T cell clones for infusion, inherent with this approach, could enhance the therapeutic graft-versus-tumor effect while possibly decreasing the risk of graft-versus-host disease.
The pathogenesis of vitiligo is complex and not well understood. Genes play a role in all aspects of vitiligo pathogenesis, and studies are ongoing to identify these genes and understand their biology. There is a body of interlocking, compelling evidence supporting an autoimmune basis for most or all cases of generalized vitiligo. The development of an autoimmune disease generally involves three components; the immune system, environmental triggers and other exogenous precipitating factors, and the target tissue. In vitiligo, precipitating factors could induce melanocyte damage in genetically susceptible individuals and consequent cell death, loss of tolerance, and induction of melanocyte-directed autoimmunity. Future research will more precisely define the multiple biological events that regulate development of vitiligo.
autoimmunity; leukoderma; melanocytes; pigmentation
Both alopecia areata (AA) and vitiligo are autoimmune diseases, and their coexistence in the same patient is not uncommon, as vitiligo has been reported to occur in 4.1% of patients of AA. We present a case of a 15-year-old male child who had vitiligo and later developed AA over the existing lesions of vitiligo over face and scalp and have attempted to elucidate the current understanding of mechanisms of coexistence of these two diseases. Our case lends support to the hypothesis that AA and vitiligo share a common pathogenic pathway including autoimmune response against some common antigens like those derived from the bulb melanocytes. Stimulation of proinflammatory T-helper(Th)-1 cell mediated immunological response or inactivation of a suppressor T-cell mediated response could be the common underlying phenomenon. However, the striking rarity of colocalization of these two diseases has led to the recent debate over current understanding of their pathogenesis, and whether this association is merely a coincidence. As both AA and vitiligo are frequent and chronic dermatological disorders, it is of utmost importance to gain more understanding into their pathogenic mechanisms so that more definitive treatment modalities may be devised and the quality of life of these patients can be improved.
Alopecia areata; colocalization; vitiligo
Vitiligo is characterized by the death of melanocytes in the skin. This is associated with the presence of T cell infiltrates in the lesional borders. However, at present, there is no detailed and systematic characterization on whether additional cellular or molecular changes are present inside vitiligo lesions. Further, it is unknown if the normal appearing non-lesional skin of vitiligo patients is in fact normal. The purpose of this study is to systematically characterize the molecular and cellular characteristics of the lesional and non-lesional skin of vitiligo patients.
Methods and Materials
Paired lesional and non-lesional skin biopsies from twenty-three vitiligo patients and normal skin biopsies from sixteen healthy volunteers were obtained with informed consent. The following aspects were analyzed: (1) transcriptome changes present in vitiligo skin using DNA microarrays and qRT-PCR; (2) abnormal cellular infiltrates in vitiligo skin explant cultures using flow cytometry; and (3) distribution of the abnormal cellular infiltrates in vitiligo skin using immunofluorescence microscopy.
Compared with normal skin, vitiligo lesional skin contained 17 genes (mostly melanocyte-specific genes) whose expression was decreased or absent. In contrast, the relative expression of 13 genes was up-regulated. The up-regulated genes point to aberrant activity of the innate immune system, especially natural killer cells in vitiligo. Strikingly, the markers of heightened innate immune responses were also found to be up-regulated in the non-lesional skin of vitiligo patients.
Conclusions and Clinical Implications
As the first systematic transcriptome characterization of the skin in vitiligo patients, this study revealed previously unknown molecular markers that strongly suggest aberrant innate immune activation in the microenvironment of vitiligo skin. Since these changes involve both lesional and non-lesional skin, our results suggest that therapies targeting the entire skin surface may improve treatment outcomes. Finally, this study revealed novel mediators that may facilitate future development of vitiligo therapies.
Vitiligo is an autoimmune disease presenting with progressive loss of skin pigmentation. The disease strikes 1% of the world population, generally during teenage years. The progressive loss of melanocytes from depigmenting vitiligo skin is accompanied by cellular infiltrates containing both CD4+ and CD8+ T lymphocytes. Infiltrating cytotoxic T cells with high affinity T cell receptors have likely escaped clonal deletion in the thymus, allowing such T cells to enter the circulation. Through the expression of CLA, these T cells home to the skin where they express type 1-cytokine profiles and mediate melanocyte apoptosis via the granzyme/perforin pathway. T cells found juxtapositionally apposed to remaining melanocytes can be isolated from the skin. Vitiligo T cells have demonstrated reactivity to antigens previously recognized as target antigens for T cells infiltrating melanoma tumors. In a comparison to existing melanoma-derived T cells, vitiligo T cells displayed superior reactivity towards melanoma cells. It is thought that genes encoding the TCRs expressed by vitiligo skin infiltrating T cells can be cloned and expressed in melanoma T cells, thereby generating a pool of circulating T cells with high affinity for their targets that can re-direct the immune response towards the tumor.
Melanocytes; T cells; T cell avidity; T cell receptors; Melanosomes; Antigen presentation
Generalized vitiligo is a common disorder in which patchy loss of skin and hair pigmentation principally appears to result from autoimmune loss of melanocytes from affected regions. We previously characterized a unique founder population in an isolated Romanian community with elevated prevalence of generalized vitiligo and other autoimmune diseases, including autoimmune thyroid disease, rheumatoid arthritis, and type I diabetes mellitus. Here, we describe a genome-wide association study (GWAS) of generalized vitiligo in 32 distantly related affected patients from this remote village and 50 healthy controls from surrounding villages. Vitiligo was significantly associated with single-nucleotide polymorphisms (SNPs) in a 30-kb LD block on chromosome 6q27, in close vicinity to IDDM8, a linkage and association signal for type I diabetes mellitus and rheumatoid arthritis. The region of association contains only one gene, SMOC2, within which SNP rs13208776 attained genome-wide significance for association with generalized vitiligo (P = 8.51×10−8) at odds ratio 7.445 (95% confidence interval=3.56–15.53) for the high-risk allele and population attributable risk 28.00. SMOC2 encodes a modular extracellular calcium-binding glycoprotein of unknown function. Our findings indicate that SMOC2 is a risk locus for generalized vitiligo and perhaps other autoimmune diseases.
Generalized vitiligo is the most common pigmentation disorder, the result of autoimmune loss of melanocytes from the skin and hair, with a high frequency of other autoimmune diseases in vitiligo patients and their relatives. We previously reported the linkage signals on chromosomes 1, 7, and 17 in Caucasian families with generalized vitiligo and associated autoimmune diseases and identified the risk loci of chromosomes 17 and 1 as NLRP1 (NALP1) and FOXD3, respectively. Here, we describe fine-scale genetic association analyses in two independent series of Caucasian multiplex families, refining localization of the chromosome 7 locus and a locus on chromosome 9. Three susceptibility signals, represented by single-nucleotide polymorphisms (SNPs) rs6960920 in 7p13, rs734930 in 7q11, and rs4744411 in 9q22, were significantly associated with vitiligo and other autoimmune diseases. We also detected significant three-way interaction effects of chromosome 7 SNP rs6960920, chromosome 9 SNP rs4744411, and NLRP1 SNP rs6502867 on both the vitiligo phenotype and an expanded autoimmune disease phenotype, and significant three-way interaction effects of both chromosome 7 SNPs and NLRP1 SNP rs6502867 on the vitiligo phenotype. These support the validity of the chromosomes 7 and 9 linkage/association signals and underscore the utility of gene-gene interaction analysis in characterizing the genetic effects of candidate association signals.
Generalized vitiligo is a common autoimmune disease in which acquired patchy depigmentation of skin, hair, and mucous membranes results from loss of melanocytes from involved areas. Previous genetic analyses have focused on vitiligo susceptibility, and have identified a number of genes involved in disease risk. Age of onset of generalized vitiligo also involves a substantial genetic component, but has not previously been studied systematically. In this study, we report a genome-wide association study of vitiligo age of onset in 1,339 generalized vitiligo patients, with replication in an independent cohort of 677 cases. We identified a quantitative trait locus for vitiligo age of onset in the major histocompatibility complex (MHC) class II region, located near c6orf10-BTNL2 (rs7758128; P = 8.14×10−11), a region that is also associated with generalized vitiligo susceptibility. In contrast, there was no association of vitiligo age of onset with any other MHC or non-MHC loci that are associated with vitiligo susceptibility. These findings highlight the differing roles played by genes involved in vitiligo susceptibility versus vitiligo age of onset, and illustrate that genome-wide analyses can be used to identify genes involved in quantitative aspects of disease natural history, as well as disease susceptibility per se.
During the 2011 International Pigment Cell Conference (IPCC), the Vitiligo European Taskforce (VETF) convened a consensus conference on issues of global importance for vitiligo clinical research. As suggested by an international panel of experts, the conference focused on four topics: classification and nomenclature; definition of stable disease; definition of Koebner’s phenomenon (KP); and ‘autoimmune vitiligo’. These topics were discussed in seven working groups representing different geographical regions. A consensus emerged that segmental vitiligo be classified separately from all other forms of vitiligo and that the term ‘vitiligo’ be used as an umbrella term for all non-segmental forms of vitiligo, including ‘mixed vitiligo’ in which segmental and non-segmental vitiligo are combined and which is considered a subgroup of vitiligo. Further, the conference recommends that disease stability be best assessed based on the stability of individual lesions rather than the overall stability of the disease as the latter is difficult to define precisely and reliably. The conference also endorsed the classification of KP for vitiligo as proposed by the VETF (history based, clinical observation based, or experimentally induced). Lastly, the conference agreed that ‘autoimmune vitiligo’ should not be used as a separate classification as published evidence indicates that the pathophysiology of all forms of vitiligo likely involves autoimmune or inflammatory mechanisms.
vitiligo; consensus conference
Generalized vitiligo is thought to have an autoimmune etiology, and has been correlated with the presence of CD8 T cells specific for melanocyte differentiation antigen. However, limited animal models for the disease have hampered its understanding. Thus, we generated TCR transgenic mice that recognize an epitope of the melanocyte protein, tyrosinase. These animals develop vitiligo with strikingly similar characteristics to the human disease. Vitiligo develops temporally and spatially, with juvenile lesions forming bilaterally in head and facial areas, and only arising later in the body of adult animals. Vitiligo is entirely dependent on CD8 T cells, while CD4 T cells exert a negative regulatory effect. Importantly, CD8 T cells can be pervasively present in the skin in the steady state without inducing vitiligo in most areas. This points to developmental differences in melanocyte susceptibility and/or immunological effector mechanisms over time, or in different body locations. Disease is strongly dependent on both IFNγ and CXCR3, while dependence on CCR5 is more limited, and both CCR4 and perforin are dispensable. Genetic ablation of CXCR3 or IFNγ also resulted in scarce CD8 T cell infiltration into the skin. Our results identify unexpected complexity in vitiligo development and point towards possible therapeutic interventions.
Human; Antigens/peptides/epitopes; MHC; Antigen presentation/processing; Tumor immunity
Nonsegmental vitiligo is a depigmented skin disorder showing acquired, progressive, and depigmented lesions of the skin, mucosa, and hair. It is believed to be caused mainly by the autoimmune loss of melanocytes from the involved areas. It is frequently associated with other autoimmune diseases, particularly autoimmune thyroid diseases including Hashimoto's thyroiditis and Graves' disease, rheumatoid arthritis, type 1 diabetes, psoriasis, pernicious anemia, systemic lupus erythematosus, Addison's disease, and alopecia areata. This indicates the presence of genetically determined susceptibility to not only vitiligo but also to other autoimmune disorders. Here, we summarize current understanding of autoimmune pathogenesis in non-segmental vitiligo.
Vitiligo is an acquired depigmenting disorder characterized by the loss of functional melanocytes from the epidermis. Although the etiology of vitiligo is unknown, over the last few years, substantial data from clinical research has greatly supported the ‘Autoimmune theory’ and this is supported by the frequent association of vitiligo with disorders that have an autoimmune origin, including Hashimoto's thyroiditis, Graves disease, type 1 insulin-dependent diabetes mellitus, and Addison's disease. As cytokines are important mediators of immunity, there is evidence to suggest that they play a major role in the pathogenesis of autoimmune diseases.
Keeping this in view we have assayed sera for cytokine IL-6, IL-2, Tumor necrosis factor (TNF)-α, and IFNγ in 80 cases of vitiligo and compared it with healthy subjects, in order to find out whether they play a role in the pathogenesis of vitiligo or not.
Materials and Methods:
Serum IL-6, IL-2, TNF-α, and IFNγ were done by the indirect enzyme linked immunosorbent assay (ELISA).
The mean serum IL-6 and IL-2 levels in the patient group were significantly higher when compared with those of the normal controls. The mean serum IFNγ level in patients with vitiligo was significantly lower than that in the control group. There was no significant difference in the serum level of TNF-α between vitiligo and healthy controls.
An increase in the production of proinflammatory cytokines such as IL-6 and IL-2 in vitiligo patients may play an important role in melanocytic cytotoxicity. Thus, we speculate that the cytokine production of epidermal microenvironment may be involved in vitiligo.
Cytokines; IFN-gamma; IL-2; IL-6; TNF-alpha; vitiligo
Generalized vitiligo is an autoimmune disease characterized by melanocyte loss, which results in patchy depigmentation of skin and hair, and is associated with an elevated risk of other autoimmune diseases.
To identify generalized vitiligo susceptibility loci, we conducted a genomewide association study. We genotyped 579,146 single-nucleotide polymorphisms (SNPs) in 1514 patients with generalized vitiligo who were of European-derived white (CEU) ancestry and compared the genotypes with publicly available control genotypes from 2813 CEU persons. We then tested 50 SNPs in two replication sets, one comprising 677 independent CEU patients and 1106 CEU controls and the other comprising 183 CEU simplex trios with generalized vitiligo and 332 CEU multiplex families.
We detected significant associations between generalized vitiligo and SNPs at several loci previously associated with other autoimmune diseases. These included genes encoding major-histocompatibility-complex class I molecules (P = 9.05×10−23) and class II molecules (P = 4.50×10−34), PTPN22 (P = 1.31×10−7), LPP (P = 1.01×10−11), IL2RA (P = 2.78×10−9), UBASH3A (P = 1.26×10−9), and C1QTNF6 (P = 2.21×10−16). We also detected associations between generalized vitiligo and SNPs in two additional immune-related loci, RERE (P = 7.07×10−15) and GZMB (P = 3.44×10−8), and in a locus containing TYR (P = 1.60×10−18), encoding tyrosinase.
We observed associations between generalized vitiligo and markers implicating multiple genes, some associated with other autoimmune diseases and one (TYR) that may mediate target-cell specificity and indicate a mutually exclusive relationship between susceptibility to vitiligo and susceptibility to melanoma.
Vitiligo is a skin disease characterized by depigmentation. Its etiopathogenesis is unclear, but it has been associated with autoimmune processes. Gene polymorphisms in the tumor necrosis factor-α (TNF-α) have been associated with several imflammatory diseases. In particular, the -308G/A polymorphism in the gene promoter region has been reported to be associated with increased plasma levels of TNF-α and with an increased risk to develop autoimmune diseases. To date, this polymorphism has not been associated with vitiligo. To assess a possible association between the TNF-α -308G/A and vitiligo vulgaris (VV), 198 vitiligo patients and 395 control subjects were recruited for the study. A complete demographic and clinical profile of each case was registered to analyze the possible risk factors of vitiligo. Genomic DNA isolated from peri pheral blood was subjected to PCR-RFLP for genotyping of the TNF-α -308G/A polymorphism. Causal associations were determined by χ2 test and their respective OR was assessed in a 2×2 contingency table. When population variables of type of vitiligo, gender, age of disease onset, and active disease status were considered, an association between active VV and the TNF-α GA genotype was found (P=0.0295, OR=2.0; 95% CI 1.01-3.93). All other variables were irrelevant to vitiligo. Our data suggest a possible association between the TNF-α -308 GA genotype and the active form of VV in a Mexican population.
tumor necrosis factor-α -308G/A polymorphism; active vitiligo vulgaris; autoimmune diseases; PCR-RFLP; northeastern Mexican population
Vitiligo or leukoderma is a chronic skin condition that causes loss of pigment due to destruction of melanocytes, resulting in irregular pale patches of skin. Vitiligo is a polygenic disease and is associated with autoimmunity with an unknown etiology.
One of the candidate genes which has a strong association with several autoimmune diseases is CTLA-4 gene located in chromosome 2q33 region. We investigated the possible association between CTLA-4 gene polymorphism in exon 1 (A49G) and vitiligo in patients from South India and compared the distribution of this polymorphism to matched control groups.
Patients and Methods:
The polymorphism was detected by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method in 175 patients and 180 normal, age/ethnicity matched individuals. Consistency of genotype frequencies with the Hardy-Weinberg equilibrium was tested using a χ2 test.
There was no significant difference between the genotype (P = 0.93) and allele (P = 0.615) frequencies of CTLA-4 A49G polymorphism in patients and normal healthy individuals. However there was significant association of the CTLA-4 genotype (P = 0.02) and allelic frequency (P = 0.008) between the segmental and non-segmental sub groups within vitiligo.
Our results indicate that there is no association between CTLA-4 A49G gene polymorphism and vitiligo in southern Indian population.
Autoimmune; CTLA-4; melanocytes; polymorphism; vitiligo
Vitiligo is an acquired depigmentary disorder of the skin that results from the loss of functioning epidermal melanocytes. Most studies on vitiligo have concentrated on the abnormality of melanocytes rather than the abnormality of keratinocytes; however, epidermal melanocytes form a functional and structural unit with neighboring keratinocytes. In fact, direct cell-to cell contact stimulates in vitro proliferation of melanocytes, and growth factors produced by adjacent keratinocytes regulate the proliferation and differentiation of melanocytes. The potential role of keratinocyte-derived cytokines has also been presented. We focused on the structural changes in vitiliginous keratinocytes, which may result in loss of melanocytes, to examine the pathomechanism of vitiligo. The results of a comparison between depigmented and normally pigmented epidermis in patients with vitiligo showed that the keratinocytes in the depigmented epidermis were more vulnerable to apoptosis. Impaired Phosphatidylinositol 3-kinase (PI3K)/serine/threonine protein kinase (Akt) activation followed by reduced nuclear factor-κB activation under increased tumor necrosis factor-α levels was demonstrated as a mechanism for keratinocyte apoptosis. The role of aquaporin 3 in keratinocyte apoptosis was addressed based on the relationship between the PI3K/AKT pathway and the E-cadherin-catenin complex. Apoptotic keratinocytes induced a lower expression of keratinocyte-derived factors, including stem cell factor, in depigmented epidermis, resulting in passive melanocyte death.
Activation of PI3K/Akt; Aquaporin 3; E-cadherin-catenin complex; Keratinocyte apoptosis; NF-κB; Passive melanocyte death; Stem cell factor
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.
CD8+ T cells; melanocytes; vitiligo; cytokine
Vitiligo is an acquired pigmentary disorder of the skin that is caused by unknown factors and is characterized by white and depigmented patches that enlarge and become more numerous with time. Genetic factors, oxidative stress, autoimmunity, and neurochemical agents, such as catecholamines might also contribute to vitiligo. Cutaneous pigmentation is determined by the amounts of eumelanin and pheomelanin synthesized by the epidermal melanocytes and interference of melanocortin-1 receptor (MC1R), a G-protein coupled receptor, its normal agonist, alpha-melanocyte stimulating hormone (α-MSH), and key enzymes, such as tyrosinase, to protect against sun-induced DNA damage. The MC1R, a 7 pass trans-membrane G-protein coupled receptor, is a key control point in melanogenesis. Loss-of-function mutations at the MC1R are associated with a switch from eumelanin to pheomelanin production, resulting in a red or yellow coat color.
In this research, we aim to examine the genetic variety of MC1R and α-MSH gene in 20 Iranian vitiligo patients and 20 healthy controls.
Materials and Methods:
Analysis of the MC1R coding gene was performed with direct sequencing.
We found the following 9 MC1R coding region variants: Arg163Gl (G488A), Arg227Leu (G680A), Val 97Phe (G289T), Asp184Asn (G550A), Arg227Lys (G680A), Arg142His (G425A), Val60Leu (G178T), Val247Met (C739A), and Val174Ile (G520A). We also found 2 frameshift changes: one of them was the Insertion of C (frameshift in Pro136, stop at Trp148) and the other, Insertion of G (frameshift in Pro256, stop at Trp 333). Of all the changes, the most common was Val60Leu at 5% in patients vs 20% in controls, Val247Met at 15% in patients vs 0% in controls and Val174Ile at 15% in controls and 0% in patients. The other variants showed a frequency <5% in both patients and controls. Also in this study, we have examined the frequency of single nucleotide polymorphisms within the α-MSH genes with direct sequencing in 20 patients and 20 healthy subjects but found no changes along this gene.
We could not find any relationship between MC1R and α-MSH genes and their effect on the disease in Iranian vitiligo patients.
Vitiligo; MC1R; melanocortin 1-receptor; α-MSH; α-melanocyte stimulating hormone; variant; polymorphism
Mammalian pigmentation results from the synthesis and accumulation of photo protective epidermal melanin. Melanin was formed from the amino acid precursor L-tyrosine within specialized cells, the melanocytes. Oxidative stress has been suggested to be the initial pathogenetic event in melanocyte degeneration with H2O2 accumulation in the epidermis of patients with active disease. Auto immunity has been also suggested as another hypothesis in the pathogenesis of depigmentation disorders. Topical corticosteroids and phototherapy as common treatment modalities have been prescribed in patients with vitiligo. However, they are often not effective and safe (epidermal atrophy). Therefore, research for alternative therapies continues.
To evaluate the beneficial effects of a supplementation with antioxidant vitamins (A, C, E) and minerals (zinc, selenium) for vitiligo treatment.
Forty experimental autoimmune vitiligo mice C57BL6, aged from 5 to 12 months showing visible signs of induced vitiligo, were sequentially randomized into five parallel groups (8 mice per group). Each group mice was allocated an identical pre coded cage. the first group (SZV) received the ED + 1,4 g zinc (Zn) + 0.04 g selenium (Se) + vitamins (A 118 UI, C 8,5 mg, E 5,4 UI) /kg diet, the second group (PSZV) received the ED + 1,4 g zinc (Zn) + 0.04 g selenium (Se) + vitamins (A 118 UI, C 8.5 mg, E 5,4 UI)/kg diet + Polyphenol orally, the group 3 (PSZ) received the ED + green tea decoction prepared from 100 g/l (polyphenol orally) + 1,4 g Zn + 0.04 g Se, the 4 (P) received the ED + green tea decoction prepared green tea decoction prepared from 100 g/l, the control group 5(C) received the ED + distilled water. Cure was defined as repigmentation of treated sites. Photographic and optical techniques were used both at the baseline and on weekly basis.
By the end of the study, mices showed visible repigmentation. Using the investigator's global assessment, therapeutic success in terms of a clear repigmentation documented in 70% of treated mice.
Our findings suggest that an antioxidant supplementation is significantly beneficial in contributing superior clinical efficacy to cure vitiligo.
Polyphenol; vitiligo; vitamins
Vitiligo is a common skin disorder, characterized by progressive skin
de-pigmentation due to the loss of cutaneous melanocytes. The exact cause of
melanocyte loss remains unclear, but a large number of observations have
pointed to the important role of cellular immunity in vitiligo
In this study, we characterized T cell and inflammation-related dermal
dendritic cell (DC) subsets in pigmented non-lesional, leading edge and
depigmented lesional vitiligo skin. By immunohistochemistry staining, we
observed enhanced populations of CD11c+ myeloid dermal DCs and
CD207+ Langerhans cells in leading edge vitiligo biopsies.
DC-LAMP+ and CD1c+ sub-populations of dermal DCs expanded
significantly in leading edge and lesional vitiligo skin. We also detected
elevated tissue mRNA levels of IL-17A in leading edge skin biopsies of
vitiligo patients, as well as IL-17A positive T cells by
immunohistochemistry and immunofluorescence. Langerhans cells with activated
inflammasomes were also noted in lesional vitiligo skin, along with
increased IL-1ß mRNA, which suggest the potential of Langerhans cells
to drive Th17 activation in vitiligo.
These studies provided direct tissue evidence that implicates active Th17
cells in vitiligo skin lesions. We characterized new cellular immune
elements, in the active margins of vitiligo lesions (e.g. populations of
epidermal and dermal dendritic cells subsets), which could potentially drive
the inflammatory responses.
Generalized vitiligo is an autoimmune disease of skin pigmentation that is associated with increased prevalence of other autoimmune diseases, particularly autoimmune thyroid disease (AITD; principally Hashimoto's disease and Graves' disease), both in vitiligo patients and their close relatives, suggesting a heritable predisposition involving, in part, shared susceptibility genes.
This review summarizes current knowledge of vitiligo epidemiology and genetics, highlighting recent findings from genome-wide approaches to disease gene identification, emphasizing susceptibility loci shared with other autoimmune diseases, particularly AITD, as well as some important differences.
Inherited susceptibility to generalized vitiligo involves a number of specific genes, many of which are shared with other autoimmune diseases that are epidemiologically associated with vitiligo, including AITD, confirming a longstanding hypothesis about the genetic basis of these disorders. These genes provide potential therapeutic targets for novel approaches to treatment as well as for approaches to presymptomatic diagnosis and disease prevention in individuals with inherited susceptibility to this group of autoimmune diseases.