Relationship Between Regulatory T Cell And Foxp3 Gene Polymorphism And Vitiligo

BackgroundsVitiligo is an acquired, non-contagious disorder in which progressive, patchy loss of pigmentation of skin, results from loss of melanocytes from the cutaneous epidermis. The onset age is most frequently found in the 2nd decade of life, with a 0.5-2% incidence worldwide, without predilection for sex or race. As the pathogenesis of vitiligo is still not clear, many different etiologic hypotheses have been suggested for vitiligo, the biochemical hypothesis, the neural hypothesis, the autoimmune hypothesis, a complex biochemical imbalance with defective free-radical defense, the most compelling of which involves a combination of environmental and genetic factors interacting to contribute to autoimmune melanocyte destruction. Although all these hypotheses are based on some corroborating evidence, none of them can fully explain the disease. More typically, however, familial aggregation of generalized vitiligo cases takes a non-Mendelian pattern that is suggestive of polygenic, multifactorial inheritance.Recently, the autoimmune aspects of vitiligo have become more popular. There exist autoantibodies and autoreactive T cells in vitiligo patients that have cytotoxic effects upon pigment cells. Lots of studies that shows immune cells play a role in vitiligo, including the changes in the proportion of CD4⁺ and CD4⁺/CD8⁺. The discovery of regulatory T cells has widened our views on the immunological regulation and periphery self-tolerance. Regulatory T cells can repress the activation of CD4⁺CD25- cells, CD4⁺ cells, CD8⁺cells, and maintain normal immune homeostasis. It has been reported that the suppressive activity of Treg cells in suppressing the activation of CD4⁺ effect cells declined in patients with autoimmune diseases. All these findings indicated that regulatory T cells may involved in the pathogenesis of vitiligo.Among the strongest support for an autoimmune origin of generalized vitiligo is its epidemiological association with other autoimmune diseases. In several studies vitiligo has been associated with autoimmune thyroid disease, pernicious anemia, Addison's disease, and perhaps alopecia areata. NALP1 and PTPN22 gene have been recognized as susceptibility genes for vitiligo and vitiligo associated autoimmune disease. However, the vitiligo associated diseases have inheritance nature. So, it has been proposed that genetic predisposition and hereditary susceptibility implied in the pathogenesis of vitiligo. Several genes that have a role in autoimmune disease may increase the risk of vitiligo.FOXP3 gene specifically expressed in CD4⁺CD25⁺ T cells and played an important role in the development and function of regulatory T cells. It has been recognied as key regulatory molecular for Treg cells. Mutations of the human FOXP3 gene, the ortholog of murine Foxp3, were immediately found to be the cause of a similar human disease called IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome), which is characterized by autoimmune disease in multiple endocrine organs (such as T1D and thyroiditis), IBD, and severe allergy. It has been reported that a functional polymorphism in the promoter/enhancer region of the FOXP3/Scurfin gene associated with type 1 diabetes. So far, no studies have investigated the proportion changes of CD4⁺CD25⁺ T cells in generalized vitiligo or the association between the polymorphism of FOXP3 gene and the susceptibility of vitiligo.ObjectiveTo observe the proportion changes of CD4⁺CD25⁺ T cells and CD4⁺CD25⁺FOXP3⁺ nTreg cells in active generalized vitiligo.To analyze the association between the susceptibility of vitiligo patients in the Han nationality of Chinese and the polymorphisms in exon -3279, intron -6054 and exon -924 of Foxp3( forkhead/ winged helix transcription factor) gene. The results might help us understand the genetic and immunological inducements of vitiligo. They could also help us in understanding the diagnosis and prognosis of vitiligo.MethodsWe collected forty five patients with untreated active generalized vitiligo in our clinic from August, 2007 to November, 2007. Peipberal blood mononuclear cells (PBMCs) were isolated and used to examin the changs in the proportions of CD4⁺CD25⁺ Treg cells. Twenty four health people were enrolled in normal control group.Under case-control design, Vitiligo patients and unrelated Chinese Han nationality population were recruited to extract genomic DNA from peripheral blood samples. Genotypes were detected using PCR-SSP techniques. By analyzing the polymorphism in exon -3279, exon -6054 and exon -924 of Foxp3( forkhead/ winged helix transcription factor) gene of vitiligo patients and the health people, we analyzed the association between polymorphism in FOXP3 and vitiligo susceptibility. Results1. Regulatory T cells testsThe percentages of CD4⁺CD25⁺Regulatory T cells and CD4⁺CD25⁺FOXP3⁺ natural Regulatory T cells in patients with active vitiligo were high than that in normal control .The difference was significant (P <0.05). The proportion of CD4⁺CD25⁺Regulatory T cells in CD4⁺ cells in periphery blood of patients with active vitiligo was higher than that in normal control with statistically difference (P< 0.01). The proportion of CD4⁺CD25⁺FOXP3⁺ natural Regulatory T cells in CD4⁺ CD25^high Regulatory T cells in periphery blood of patients with active vitiligo was lower than that in normal control with statistically difference (P< 0.01).2. Polymorphisms in FOXP3 gene2.1. The univariate analysis showed a significant difference in FOXP3 gene polymorphism between vitiligo patients and healthy controls. It seemed that individual carrying AA,AA and GG genotype would be more susceptible to vitiligo. And there was significant difference in intron -6054 of FOXP3 gene polymorphisms between vitiligo patients and healthy controls.2.2. In exon -6054 of FOXP3 gene polymorphisms, no matter what age, sex or type the patients were, individual carrying AA genotype would be more susceptible to vitiligo.2.3. In exon -3279 of FOXP3 gene polymorphisms, the male carrying AA genotype would be more susceptible to vitiligo. No matter how old, or the type the patients were, individual carrying AA genotype would be more susceptible to vitiligo.2.4. In exon -924 of FOXP3 gene polymorphisms, the male carrying GG genotype would be more susceptible to vitiligo. No matter how old the patients were, individual carrying GG genotype would be more susceptible to vitiligo. The one carrying GG genotype would be more susceptible to non-segment vitiligo.ConclusionsFor the first time, we observed the proportion changes of CD4⁺CD25⁺ T cells and CD4⁺CD25⁺FOXP3⁺ nTreg cells in active vitiligo patients, which indicated the immune disequilibrium of vitiligo patients. Cell-mediated immunity, especially the regulatory T cells, may play a role in the pathogenesis of vitiligo. The polymorphisms of FOXP3/Scurfin gene (exon -3279, exon -6054 and exon -924) appear to confer a significant susceptibilityto vitiligo in Chinese Han nationality population. Take all the results together, our study demonstrated the immune and inheritance aspects of vitiligo, and this may help us in the treatment of vitiligo.