Assessment of Programmed Cell Death (PD-1) and its Ligand’s (PD-L1) levels in vitiligo

Abstract Background : Programmed cell death 1 (PD-1) is a cell surface protein that serves as an immune checkpoint in conjunction with its two ligands, PD-L1 and PD-L2. Recently, there has been a lot of interest in the role of the PD-1/PD-L1 pathway in immunoregulation. When PD-1/PD-L1 pathway inhibitors were used in cancer therapy, the observed aggravation of the pre-existing autoimmune disease and the emergence of autoimmune-like symptoms shed light on the potential therapeutic role of increasing PD-L1 expression or activating PD-1 in the fight against diseases with autoimmune pathology, including vitiligo. The present study aimed to assess both PD-1 and PD-L1 levels in vitiligo patients’ marginal and non-lesional biopsies in comparison with normal controls and to correlate them with disease parameters. Methods : Thirty vitiliginous patients and 30 age and sex-matched controls were included. Full history and clinical examination were done and tissue levels of PD-1 and PD-L1 were measured by ELISA from lesional and non-lesional biopsies. Results : Levels of tissue PD-1 in marginal biopsies were significantly higher than in non-lesional biopsies (p< .001) and significantly higher than the control PD-l level (p< .001). Non-lesional PD-1 level was also significantly higher than the control PD-l level (p< .001). A statistically significant positive correlation was found between marginal and non-lesional PD-1 levels; (rho=0.792, p< .001). Levels of tissue PD-1 in non-lesional biopsies were significantly higher than in controls (P<0.001) and levels of tissue PD-L1 in non-lesional biopsies were significantly lower than in controls (P<0.001). Non-lesional PD-L1 level was also significantly higher than the control PD-Ll level (p< .001).