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 PBMC (n=4) from 4 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. IPA and qPCR validation were performed for DEGs.

Results: 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. 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. qPCR 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.