Involvement of Different Genes Expressions during Immunological and Inflammatory Responses in Vitiligo.

Abstract

Vitiligo is a condition of the skin distinguished by hypo-pigmentation. Etiology of this disorder is unknown, and several theories and mechanisms have been hypothesized. The inflammatory response in vitiligo is thought to be mediated by polymorphism in genes such as FOXP3, ACE, APE, GSTP1, TLR, SOD, CTLA-4, TAP/LMP gene cluster, etc. Theories including reactive oxygen species model, Nrf2-antioxidant response element (ARE) pathway, WNT pathway, tyrosinase activity, biochemical, molecular, and cellular alterations have been hypothesized to explain vitiligo pathogenesis. Melanosomal proteins are involved in antigen processing. The antigens are expressed to the T-cells in the form of peptides with HLA class II molecules. T-cells are activated in response to the discharge of co-stimulatory molecules such as LFA-3 as well as ICAM-1. An adaptive immune response is thus elicited, and the melanocytes eventually die or start malfunctioning and the skin undergoes hypo-pigmentation. IFN-γ is known to be a melanocyte inhibitor of paracrine origin; it is clearly involved in the early onset of symptoms of vitiligo disease. The surge in the IFN-γ levels mediates augmented expression of ICAM-1 molecule on the melanocytes, thereby establishing cytokine-mediated destruction of melanocytes. Mainly, mediators released by melanocytes and the functionality of keratinocytes decrease the disease activity. Such mediators include ET-1 as well as SCF, increase the pigmentation particularly when a patient is given with the UVB treatment. By scavenging ROS and screening UV radiation, melanin limits the damage caused to the cutaneous cells by UV radiation. Various immune responses play important roles in vitiligo.