الفهرس 
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Abstract
Vitiligo is an acquired, progressive, multifactorial, depigmenting disorder of the skin and its appendages, characterized by the appearance of circumscribed white macules in the skin due to chronic, progressive loss of functional melanocytes in the epidermis. CD8+ effector memory T cells recognized by its expression of Natural killer group 2D (NKG2D) marker and the CD8+ Tissue resident memory (TRM) cells recognized by its expression of the CD49a marker are responsible for depigmentation and development of vitiligo. CD8+ effector memory T cells have been found to be of higher frequency in skin and blood of vitiligo patients and were reported to be responsible for maintenance of depigmentation, flare-up, and progression of the disease through their release of Tc1- related cytokines IFN-γ and TNF-α. Their tissue frequency has been correlated to disease activity.
Patients with vitiligo express higher levels of cytotoxic CD8+ T lymphocytes within their skin than healthy individuals. As a result, epidermis-infiltrating T lymphocytes declare an increased CD8/CD4 ratio. IL15 functions mainly in a cell contact-dependent pattern as it increases production of IFNγ, cytotoxic capacity of epidermal CD49a+ TRM cells and promotes the function of CD8+ TEM.
The aim of this study was to evaluate the frequency of NKG2D+ CD8+ effector memory T cells, CD8+CD49a+ tissue resident memory cells and CD4 to CD8 ratio in suction blister fluid in patients with non-segmental vitiligo as compared to healthy controls and determine their relation to disease activity and severity.
The current study was conducted on 40 female patients clinically diagnosed with NSV (20 active and 20 stable) compared to 20 healthy female participants (controls).
Suction blisters at the margins of vitiligo lesions were induced using the negative suction pressure of a 20‐mL syringe. The frequency of CD 314 as a marker for NKG2D group of cytotoxic effector T cells, CD 103 & CD 49a as markers for TRM group of cytotoxic T cells and CD4/CD8 ratio were determined using flowcytometry and the level of IL 15 was determined using ELISA.
Analyses of the study results revealed the followings:
• Regarding CD 314 and CD 103, active vitiligo group had a significantly higher expression of both markers than stable vitiligo and the control group. Moreover, stable vitiligo had a sign