Investigation of PD1 / PDL-1 expression in lesioned skin areas of vitiligo patients

Objective: Vitiligo is an acquired chronic pigmentation disorder that occurs as a result of functional epidermal melanocyte loss in the skin and mucous membranes. Although many studies have been done to explain the etiopathogenesis of vitiligo, it is still not fully explained. Several hypotheses are emphasized, including autoimmune theory, neural hypothesis, and self destruction hypothesis. Autoimmune theory is now thought to be the main mechanism in vitiligo. PD-1 is a highly expressed inhibitory receptor in T lymphocytes responsible for the regulation of autoimmunity and self-tolerance. Inhibitory signals provided by PD-1 and its ligands PDL-1, PDL-2 regulate central and peripheral tolerance by various mechanisms. Increasing evidence has demonstrated the role of the PD-1/PDL-1 pathway in the pathogenesis of autoimmune diseases. There have not been many studies investigating the expression of PD-1 and PDL-1 in the pathogenesis of vitiligo. In this study, we aimed to investigate the expression of PD-1/PDL-1 molecules in the lesioned skin of patients with vitiligo. Materials and Methods: Twenty-nine vitiligo patients and 15 healthy volunteers, whose diagnosis was histopathologically confirmed, aged between 18 and 65 years, were included in the study. Anti PD-1 and PDL-1 antibodies were applied to the skin biopsy samples taken from the patient and control groups. Cytoplasmic and membranous staining of PD-1 and PDL-1 was evaluated as positive. The number of immune cells stained for each case was evaluated. Stained cells were scored between <5, 5-10, 11-20,> 20,> 50. Results: The mean age of the patients was 38.79 ± 14.55, the mean age of the control group was 44.13 ± 12.35, and there was no significant difference between the patient and control groups (p=0.233). The number of PD-1 stained cells in the patient group was calculated as <5: 11 (37.9%), 5-10: 10 (34.5%), 11-20: 5 (17.2%),> 20: 3 (10.3%). In the control group, it was calculated as <5: 4(26.7%), 5-10: 5(33.3%), 11-20: 4 (26.7%), > 20: 2 (13.3%). There was no staining with PDL-1 in 27 (93.5%) patients and 14 (93.3%) controls. PDL-1 stained cell count was <5: 2 (6.5%) in the patient group and <5: 1 (6.7%) in the control group. The rate of staining with PD-1 and PDL-1 does not show a statistically significant difference between patient and control groups (p=0.831, p=0.977) (Table 3). Conclusion: PD-1 and PDL-1 expression in immune cells in lesional skin samples of vitiligo patients do not differ significantly when compared with healthy controls. Key Words: Autoimmunity, PD-1, PDL-1, vitiligo