Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Dermatology and Venerology

Background: Programmed cell death 1 (PD-1) is an immune checkpoint cell surface protein with two ligands, PD-L1 and PD-L2. PD-1/PD-L1 interactions are essential for peripheral T cell tolerance and protecting tissues from autoimmune attack. PD- 1/PD-L1 checkpoint is implicated in multiple autoimmune diseases, and recently were suggested to have a role in vitiligo development due to the high incidence of vitiligo like lesions as an adverse effect of PD-1/PD-L1 blockade. Aim of work: To assess both PD-1 and PD-L1 levels in vitiligo patients{u2019} marginal and nonlesional biopsies in comparison with normal controls, and to correlate them with disease parameters. Methods: 30 vitiliginous patients and 30 age and sex matched controls were included. Full history and clinical examination were done and tissue levels of PD1 were measured by ELISA from lesional and nonlesional biopsies. Results: Levels of tissue PD-1 in marginal biopsies were significantly higher than in nonlesional biopsies (p<{u2009}.001) and significantly higher than control PD-l level (p<{u2009}.001). Nonlesional PD-1 level was also significantly higher than control PD-l level (p<{u2009}.001). A statistically significant positive correlation was found between marginal and nonlesional PD-1 levels; (rho=0.792, p<{u2009}.001). Levels of tissue PD-L1 in marginal biopsies were significantly lower than in nonlesional skin (p<0.001) and significantly lower than in controls (P<0.001). Nonlesional PD-L1 level was also significantly lower than control PD-Ll level (p<{u2009}.001). Conclusion: PD-1/PD-L1 may be involved in the pathogenesis of vitiligo

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