Single-cell transcriptome and TCR sequencing reveals immune cell heterogeneity in the submandibular gland of SS mice

In this study, we analyzed the submandibular gland and submandibular gland-draining lymph nodes of P40-/-CD25-/- (SS mice) and P40-/-CD25+/- (control mice) using single-cell transcriptome and TCR sequencing of leukocytes. A total of 24,115 cells were obtained for analysis, of which 9,897 cells were from the submandibular gland and 14,218 cells were from the draining lymph nodes. We found that tissue-resident CD8+T cells (CD8+Trm) in the submandibular gland of SS mice expanded massively and highly expressed PD-1. These CD8+Trm cells, which highly express PD-1, exhibit clonal expansion and cytotoxicity. In addition, shared TCR analysis found that potential CD8+Trm precursor cells in the draining lymph nodes exhibited a Gzmk+Pdcd1+ phenotype. In summary, we found that PD-1+CD8+Trm cells in the submandibular gland of SS mice are potentially pathogenic and their precursors also express PD-1. Overall design: The submandibular glands and their draining lymph nodes were taken from 4 SS mice and 4 control mice around 12 weeks old. After cell isolation, CD45+ leukocytes were labeled and sorted by flow cytometry. 10X single-cell transcriptome sequencing and TCR sequencing were performed, respectively.