RNA-Seq analysis of lymphocyte-specific gene expression patterns in IgG4-related disease: comparison of submandibular glands and peripheral blood

OBJECTIVE: To clarify T/B cell-specific gene expression patterns using RNA-Seq in IgG4-related disease (IgG4-RD). METHODS: Pathologically confirmed submandibular gland (SMG) (n = 3) and peripheral blood mononuclear cells (PBMC) (n = 4) from four treatment-naïve patients with definite IgG4-RD, as well as PBMCs from primary Sjögren syndrome (pSS) (n = 3) and healthy controls (HCs) (n = 3), were collected, and subsequently Pan T and CD19+ B cells were sorted. We conducted RNA sequencing to compare the gene expressions of Pan T and CD19+ B cells in SMGs and PBMCs in IgG4-RD or IgG4-RD versus pSS and HCs in PBMCs. Ingenuity pathway analysis (IPA) and qPCR validation were performed for differentially expressed genes (DEGs). RESULTS: Principal component analysis (PCA) results showed the gene expression patterns of Pan T and CD19+ B cells derived from SMGs differed from those derived from PBMCs in IgG4-RD. However, the gene expression patterns of Pan T and CD19+ B cells derived from PBMCs were not clustered between groups. A total of 214 upregulated and 50 downregulated DEGs in Pan T cells and 630 upregulated and 109 downregulated DEGs in CD19+ B cells were identified in SMGs compared with PBMCs in IgG4-RD. The upregulated DEGs in SMGs of IgG4-RD included cytokines, chemokines, and transcription regulators. IPA for these DEGs clarified immune system-related pathways were positively regulated in SMGs compared with PBMCs in IgG4-RD. Quantitative PCR validated significantly increased mRNA expression of IL-21 and EGR2 by Pan T cells in SMGs compared with PBMCs of IgG4-RD. CONCLUSION: RNA-Seq clarified the DEGs of Pan T and CD19+ B cells from SMGs in comparison with PBMCs, which might contribute to the pathogenesis of IgG4-RD.