Site-Specific Immunological Changes Induced by Narrowband UVB in Acral and Non-Acral Vitiligo

Acral vitiligo responds less well to NB-UVB than non-acral disease, but site-specific immunologic changes during therapy are incompletely defined. The objective of this study was to compare NB-UVB-associated changes in T cell subsets and soluble mediators in acral versus non-acral vitiligo. Thirty patients with non-segmental vitiligo were enrolled. Ten underwent paired biopsies (acral and non-acral) before and after 6 months of NB-UVB for flow cytometry (Tregs, CD8+ T cells, CD8+CD45RO+ memory T cells, CD8+CD69+CD103+ TRM). Suction-blister fluid ELISA assessed IFN-γ-axis mediators (CXCR3, CXCL9, CXCL10, IFN-γ, IL-1β) in two separate groups: 10 treatment-naïve patients and 10 patients who had completed 6 months of NB-UVB therapy. Non-parametric tests used Benjamini-Hochberg FDR correction (pFDR). In paired biopsies (n = 10; CD8 n = 9), memory T cells decreased after NB-UVB in acral (4.38 [3.47-5.98] to 1.38 [0.73-2.21]; pFDR = 0.041) and non-acral lesions (5.23 [4.27-6.75] to 1.08 [0.48-2.54]; pFDR = 0.0039). TRM declined in acral (5.95 [3.17-7.41] to 0.65 [0.15-1.15]; pFDR = 0.0039) and non-acral sites (4.12 [2.50-5.57] to 0.69 [0.28-1.19]; pFDR = 0.0039). Tregs showed a site-divergent pattern: acral Tregs decreased (0.56 [0.41-0.75] to 0.08 [0.03-0.23]; pFDR = 0.0067) while non-acral Tregs increased (0.40 [0.24-0.61] to 0.95 [0.41-1.59]; pFDR = 0.0039). CD8+ T cells showed no change after correction. CXCL9 showed a non-significant decreasing trend (pFDR = 0.249); no ELISA marker remained significant after FDR correction. NB-UVB exerts a pronounced effect on cellular immunity (reductions in TRM and memory T cells) with limited cytokine suppression, with site-divergent Treg pattern.