Mechanisms of Autoimmunity in the Aire-Deficient Mouse Model of Sjogren's Syndrome

Abstract

Purpose:: To determine the cellular and humoral mechanisms mediating autoimmunity in the Aire-deficient model of Sjogren's syndrome (SS).

Methods:: Immunohistochemistry, adoptive transfer of sorted lymphocytes populations, kinetic studies of lymphocyte infiltration, and depletion of lymphoid subsets assessed the role of cellular autoimmunity mediating the SS phenotype in Aire-deficient mice. Multiplex analysis was used to investigate humoral autoimmunity in the SS model. Aire regulation of identified autoantigens was confirmed by quantitative PCR.

Results:: Aire-deficient mice show the hallmark signs of SS including keratoconjunctivitis sicca, intrapalpebral conjunctival staining, punctuate corneal epithelial erosions and filamentary keratopathy. Immunohistochemistry and kinetic studies show lymphocyte infiltration into the lacrimal and salivary glands resulting in multiple foci of CD4+ and CD8+ T-cells, and IgD+ B-cells consistent with human SS histopathology. In adoptive transfer studies, mature lymphocytes from draining lymph nodes were isolated from Aire-deficient and wild-type control mice and transferred into immunodeficient (SCID or RAG) mice. In each of the immunodeficient recipients, transferred Aire-deficient CD4+ and CD8+ T-cells and IgD+ B-cells produced SS pathology in the lacrimal and salivary glands; however, no infiltration or pathology was observed in immunodeficient recipients receiving wild-type control lymphocytes. Moreover, adoptive transfer studies with depleted populations of lymphocytes revealed that SS autoimmunity is T-cell dependent. Multiplex screening with lacrimal and salivary gland protein extracts from immunodeficient mice were probed with sera from Aire-deficient and wild-type control mice. Our results show oligoclonal reactivity with Aire-deficient serum; however, no reactivity was detected with wild-type control mouse serum. We have isolated two prominent proteins and mass spectrometry results indicate that they represent novel candidate autoantigens. Quantitative PCR analysis shows that genes for these proteins are Aire-regulated.

Conclusions:: The Aire-deficient mouse represents a novel and clinically relevant model to study the immunopathogenesis of SS. Our results suggest that SS autoimmunity is mediated by both cellular and humoral responses. These findings may facilitate the development of diagnostic biomarkers and therapeutic targets in SS patients.

Keywords: autoimmune disease • cornea: tears/tear film/dry eye • cornea: basic science