Interaction between innate immunity and Ro52-induced antibody causes Sjögren's syndrome-like disorder in mice

Abstract

Objectives Autoantibodies reactive with Ro52 are often found in sera of Sjögren’s syndrome (SS) patients. This study was undertaken to investigate the role of Ro52-induced immune responses in pathogenesis of SS. Methods New Zealand Mixed (NZM) 2758 mice were immunized with Ro52 in alum adjuvant. Control mice were immunized either with Maltose binding protein (MBP) or injected with alum alone. Mice were monitored for anti-Ro52 antibody, sialoadenitis and pilocarpine induced salivation. Antibody binding to salivary gland (SG) cells was analyzed in vivo and in vitro by immunofluorescence. Sera from immunized mice were passively transferred into untreated or alum injected NZM2758 mice. Results By day 30 post-immunization, Ro52 immunized mice generated immunoprecipitating anti-Ro52 antibodies and they had the maximum drop in saliva production. Both Ro52 immunized and control mice showed evidence of mild sialoadenitis. However, only Ro52 immunized mice had antibody deposition in their SG. Passive transfer of Ro52-immune sera induced SG dysfunction in recipient mice, only if the recipients were primed with alum. In vitro, antibodies from Ro52-immune sera were internalized by a SG cell line and this uptake was inhibited by Cytochalasin D treatment. Conclusion Our data shows for the first time that antibodies induced by Ro52 are capable of inducing SG dysfunction, and that this phenomenon is dependent on the activation of innate immunity. The mouse model described in this study implies that autoantibody deposition in the SG might be an important step in the induction of xerostomia and pathogenesis of SS.

Brief Report: Patients With Primary Sjögren's Syndrome Who Are Positive for Autoantibodies to Tripartite Motif–Containing Protein 38 Show Greater Disease Severity

“…TRIM38 is an E3 ubiquitin ligase and it has been shown to regulate inflammatory responses triggered by TNFα and IL-1B, as well as the IFN-β responses induced via TLR3 engagement (14, 15). Using an experimental mouse model system, we have recently demonstrated that mouse TRIM21 reactive antibodies penetrate live salivary gland cells ( in vitro ) (3). Thus, the possibility that anti-TRIM38 penetrate live cells and cause dysregulated inflammatory response exists.…”

“…Anti-TRIM38 reactivity was analyzed by a quantitative immunoprecipitation assay as described previously for anti-Ro52 (3). Antibody reactivity to TRIM38 was normalized against the positive control (set at 100 antibody units/ml).…”

“…Amongst the two Ro/SSA antigens, Ro60 and Ro52, autoantibodies reactive with Ro52 are present in almost 70% of pSjS patients and they are associated with a higher severity of disease (2). Our recent work in an experimental mouse model demonstrates that in conjunction with innate immunity activation, anti-Ro52 can directly induce salivary gland dysfunction (3). …”

What can Sjögren's syndrome-like disease in mice contribute to human Sjögren's syndrome?

“…The major drawback to these models is our relatively limited knowledge about disease-relevant auto-antigens in SS, thus the selected extrinsic factor is often of personal bias. Currently, four such models have been generated: BALB/c mice immunized with 60-kDa Ro peptides or New Zealand Mixed (NZM) 2758 mice immunized with Ro-60 or Ro52 antigen [18,19], C57BL/6- M3r −/− mice vaccinated with muscarinic acetylcholine type-3 (M3R) receptor peptides [20], PL/J mice immunized with carbonic anhydrase-II (CA-II) peptides [21], and C57BL/6 mice intra-peritoneally injected with murine cytomegalovirus [22]. The first three models are based on the fact that SS patients generate autoantibodies to these three tissue proteins, while the latter model is based on the concept that a virus may be an underlying cause of SS.…”

Pulmonary manifestations of Sjögren's syndrome

“…B-cell demethylation [13], activation and proliferation [14] are abnormal, and activated B-cells promote plasma cell secretion of anti-Ro (SSA) and anti-La (SSB) autoantibodies directed to the small cytoplasmic RNP-bound peptides SSA-60kD, SSA-52kD and SSB-48kD [15]. It is noteworthy that anti-Ro52 autoantibodies have only recently been proven to be able to directly cause gland dysfunction in mice [16]. The role of T-cells in Sjögren's syndrome has been extensively studied and reviewed [10] with divergent conclusions, especially regarding the roles of regulatory T-cells and T-helper 17 cells [17], but T-cell activation and cytotoxicity are undeniable.…”