Defining Cell Type-specific Immune Responses in Allergic Contact Dermatitis by Single-cell Transcriptomics
In brief, skin resident cells were isolated from ear skin of mice and 10x Genomics single cell RNAseq was applied to identify distinct cell populations. Low quality cells and outliers were discarded, and only ~27600 viable cells were used for downstream analysis. Unsupervised clustering and gene expression were visualized with the Seurat on R studio, and assignment of cell clusters was based on expression of validated marker genes. Subsequent in-depth analysis was assisted by GENE DENOVO Inc (Guangzhou, China). Overall, We found that hapten application in pre-sensitized mice resulted in rapid infiltration of IFN?-producing T cells, IL4- and IL13-producing basophils, and IL1ß-producing neutrophils and macrophages. Sc-RNAseq identified a cluster of dermal fibroblasts enriched with IFN? pathway signature and expressed high level of Cxcl9/10. In vitro, IFN?–primed dFBs shifted the T cell Th1/Th2 polarization balance towards the Th1 phenotype through a CXCR3-dependent mechanism. Topical application of birch sap extract selectively blocked T cell-dFB interaction, suppressed Th1 cell activation and alleviated skin inflammation in the ACD model. Overall design: Ear skin biopsies were collected from 2 groups, Healthy control and DNFB-induced ACD  topically applied  DNFB-induced ACD 7~8 weeks old ICR mice.