The association between Interleukin (IL)-4 gene intron 3 VNTR polymorphism and alopecia areata (AA) in Turkish population Göknur Kalkan a, ⁎, Nevin Karakus b , Yalçın Baş a , Zennure Takçı a ,Pınar Özuğuz c , Ömer Ateş b , Serbulent Yigit b a Gaziosmanpasa University, School of Medicine, Department of Dermatology, Tokat, Turkey b Gaziosmanpasa University, School of Medicine, Department of Medical Biology, Tokat, Turkey c Afyon Kocatepe University, School of Medicine, Department of Dermatology, Afyon, Turkey abstract article info Article history: Accepted 29 May 2013 Available online 4 July 2013 Keywords: Alopecia areata IL-4 Polymorphism Alopecia Genetic skin disorders Objective: Alopecia areata (AA) is hypothesized to be an organ-specific autoimmune disease of hair follicles mediated by T cells. As immunological and genetic factors have been implicated in the pathogenesis of AA, the purpose of the present study was to investigate possible associations between the functional Interleukin (IL)-4 gene intron 3 VNTR polymorphism and AA susceptibility and disease progression in Turkish popula- tion. Methods: The study group consisted of 116 unrelated patients with AA and 125 unrelated healthy controls. Genomic DNA was isolated and IL-4 gene 70 bp VNTR polymorphism determined by using polymerase chain reaction (PCR) with specific primers. Results: No association was observed between AA patients and controls according to genotype distribution (p = 0.051). The allele distribution of IL-4 gene intron 3 VNTR polymorphism was statistically different be- tween AA patients and control group (p = 0.026). The frequency of P1 allele in patients was significantly higher than that in the control group. When the P2P2 genotype was compared with P1P2 + P1P1 genotypes, a statistically significant difference was observed between patients and controls (p = 0.036). Intron 3 VNTR polymorphism in the IL-4 gene was found to be associated with AA susceptibility in Turkish population. Conclusion: The results suggest that IL-4 VNTR polymorphism in the intron 3 region may be a risk factor for the development of AA among Turkish population. This is the first to report that intron 3 VNTR polymor- phism in the IL-4 gene is associated with AA susceptibility. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Alopecia areata (AA) is a common and genetically complex hair loss disorder that affects approximately 1–2% of the general population. AA af- fects both sexes and all age groups (Safavi et al., 1995). Oval patches of non-scarring hair loss which has a sudden onset and recurrent course forms are the most familiar clinical appearance of AA (Martinez-Mir et al., 2007). The exact aetiopathogenesis of AA remains unknown. Howev- er, AA is thought to be a tissue-specific autoimmune disease directed against the hair follicle causing the patient to develop antibodies to their own hair follicle structures and suppressing or stopping hair growth (Tobin, 2003). The strong association between AA and autoimmune dis- eases supports this idea (Garg and Messenger, 2009). AA hair follicles are surrounded by an immune infiltrate with activated T-helper cells (Th cells), cytotoxic T cells (TC cells) and natural killer (NK) cells, charac- terized as a Th1-type inflammatory response (Gilhar et al., 1999; Gilhar et al., 2003). Approximately 20% of affected people have a positive family history of the disease, suggesting a genetic predisposition. Hence, AA can be considered a genetically determined immune-mediated disorder (Garg and Messenger, 2009). Interleukin-4 (IL-4) is a key cytokine secreted by Th2 lymphocytes, eosinophils and mast cells (Rocken et al., 1996) and induces the activa- tion and differentiation of B cells and the development of the Th2 subset of lymphocytes. It has cytotoxic, anti-tumor and numerous anti- inflammatory effects (Sobti et al., 2010). The biological actions of IL-4 include stimulation of IgE and mast cell eosinophil-mediated reactions. IL-4 is the principal cytokine that stimulates B-cell immunoglobulin heavy-chain switching to the IgE isotype (Del Prete et al., 1988). It has been demonstrated that an imbalance between Th1 and Th2 cytokine Gene 527 (2013) 565–569 Abbreviations: AA, Alopecia areata; IL, interleukin; PCR, polymerase chain reaction; VNTR, variable number of tandem repeat; Th cells, T helper cells; TC cells, cytotoxic T cells; NK, natural killer; TNF, tumor necrosis factors alpha; AT, alopecia totalis; AU, al- opecia universalis; SD, standard deviation; SPSS, Statistical Package for the Social Sci- ences; ANOVA, analysis of variance; OR, odds ratio; CI, confidence interval; HLA, human leukocyte antigen; SNPs, single-nucleotide polymorphisms; RA, rheumatoid ar- thritis; ESRD, end-stage renal disease; SLE, systemic lupus erythematosus; MS, multiple sclerosis. ⁎ Corresponding author at: Department of Dermatology, Gaziosmanpasa University School of Medicine, Tokat, 60100, Turkey. Tel.: +90 505 265 32 71. E-mail address: goknurkalkan@yahoo.com (G. Kalkan). 0378-1119/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gene.2013.05.086 Contents lists available at SciVerse ScienceDirect Gene journal homepage: www.elsevier.com/locate/gene