Wang, Y.; Liang, G.; Zhao, C.; Wei, Q.; Feng, S.

Bullous Pemphigoid (BP) triggers profound functional changes in both non-immune and immune cells in the skin and circulation, yet the underlying mechanisms remain elusive. In this study, we conducted single-cell transcriptome analysis on donor-matched lesional and non-lesional skin, as well as blood samples from BP patients. Lesional skin non-immune cells coordinately upregulated metabolism, wound healing, immune activation, and cell migration associated pathways. Skin LAMP3+ DCs derived from cDC2 exhibited higher pro-inflammatory signatures than those from cDC1, and VEGFA+ mast cells driving BP progression, were predominantly from lesional skin. As BP patients transition from active to remission stages, blood B cell function shifts from differentiation and memory formation to heightened type 1 interferon signaling and reduced IL-4 response. Blood CX3CR1+ZNF683+ and LAG3+ exhausted T cells exhibited the highest TCR expansion among clones shared with skin CD8+T cells, suggesting they likely represent BP-reactive cells fueling skin CD8+T cell clonal expansion. Clinical parameters for BP severity correlated positively with blood NK cell IFN-gamma production, whereas correlated negatively with NK cell AREG production. In lesional skin, NK cell-keratinocyte interactions exhibited reduced AREG-EGFR and enhanced IFNG-IFNGR1/2 signaling. NK cell-derived AREG mitigates IFN-gamma-induced keratinocyte apoptosis, highlighting a crucial balance between AREG and IFN-gamma in BP progression. These results reveal significant functional shifts in BP pathology within skin and blood cells and suggest new therapeutic targets for disease management.