Merri-Grace Allred and Scott Lieberman, University of Iowa, Iowa City, IA
Background/Purpose: Sjogren's disease is a chronic autoimmune disease autoimmune disease characterized by foci of inflammation of the lacrimal and salivary glands. As disease progresses, B cells accumulate in the glands and produce antibodies resulting in further destruction of the tissue and gland dysfunction. Male non-obese diabetic (NOD) mice spontaneously develop autoimmunity of the lacrimal glands. Disruption of the type I interferon (IFN) signaling pathway protects NOD mice from developing lacrimal gland disease1. While the impact of B cells later in disease has been well-characterized, the role of B cells in early disease development has not been defined. The goals of this study include defining the pathogenic role of B cells in lacrimal gland disease development including the potential influence of type I IFN signaling in driving B cell pathogenicity.
Methods: NOD mice spontaneously develop lacrimal gland inflammation as early as 5-6 weeks with increased inflammation over time. Ifnar1-mutant (IFNAR1 KO) NOD mice generated by CRISPR/Cas9. Mice were maintained in our facility and used in accordance with the University of Iowa Animal Care and Use Committee Guidelines. Differential gene expression was determined using the Mouse Autoimmune Profiling panel, Nanostring nCounter analysis system, and Rosalind online analysis platform to compare whole-tissue RNA from lacrimal glands of 6- and 10-week-old NOD mice. Bulk spleen cells were adoptively transferred from WT and KO donor mice to NOD-SCID recipients. Flow cytometry was utilized to define IFNAR1 expression and B cell phenotyping from gland-infiltrating and lymph node cells. TSNE plots were generated using FlowJo plugin with learning rate, perplexity, and iterations adjusted according to Belkina et al2. In vitro experiments utilized bulk or magnetically sorted spleen cells and were treated with IFNα.
Results: Lacrimal gland gene expression studies demonstrated that genes associated with B cell receptor signaling, lymphocyte trafficking and antigen presentation were upregulated at 10 weeks compared to 6 weeks. Many of these genes were present in previously published RNASeq data identifying genes that are upregulated in older (20+ week-old) WT versus IFNAR1-KO NOD mice. This suggests that type l IFN signaling drives key inflammatory pathways including B cell-associated pathways early in disease. Adoptive transfer studies demonstrated decreased disease when donor cells lacked IFNAR1 expression compared to WT donor cells, but this difference was abrogated when magnetically purified T cells were transferred suggesting a type I IFN dependent pathogenic role on a non-T cell population. The largest non-T cell population in these studies were B cells. In vitro studies suggest that B cell phenotype can be shaped by IFNα in a dose dependent manner.
Conclusion: Type l IFN signaling drives the development of lacrimal gland autoimmunity in NOD mice. Type l IFN signaling plays a role in shaping B cell phenotype and function in early lacrimal gland disease. The expression of IFNAR1 on donor cells exacerbates disease only when B cells are present. Ongoing in vivo studies will interrogate the impact of IFNAR1 expression on B cell trafficking to the lacrimal glands.