Characterization of T cell receptor repertoire and anti-Ro/SSA autoantibodies in relation to sialadenitis of NOD mice

Identification of Fangji Huangqi Tang as a potential herbal formula for Sjogren syndrome treatment via network pharmacology and experimental validation

Fangji Huangqi Tang (FHT) is a well-known Chinese herbal formula that is prescribed as treatment for rheumatoid diseases. In this study, we aimed to investigate the potential therapeutic targets, efficacy, and safety of FHT in the treatment of Sjogren's syndrome (SS). The Gene Expression Omnibus (GEO) database was used to screen differentially expressed genes (DEGs) in SS. Further, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to explore the potential biological functions of the DEGs. Subsequently, an FHT-herb-active compound-target network was constructed to identify the relationship between the active compounds in FHT and the related targets. Then, enrichment analysis involving the DEGs and protein-protein interaction (PPI) network analysis were performed to analyze the biological functions of potential targets and screen hub genes. Further, molecular docking was employed to verify the binding affinity between the active compounds and the hub targets, and in vivo experiments involving NOD/LtJ mice were conducted to verify the therapeutic effects of FHT on SS-like symptoms. Finally, inhibition of PIK3CK/Akt pathway by FHT was validated by WB and rt-qPCR. A total of 1836 DEGs were identified in SS based on the GSE159574 dataset, and 114 targets of the active compounds in FHT were screened. Further, via network pharmacology analysis and molecular docking, six active compounds and five hub targets were obtained, and enrichment analysis showed that the anti-SS effect of FHT was predominantly associated with immune cells, such as T cells and neutrophils. In vivo, FHT effectively reduced lymphocyte infiltration foci, increased saliva flow rate, and inhibited increases in the levels of SS-related autoantibodies (anti-SSA and anti-SSB). Furthermore, the biosafety of FHT was verified via the serological examination of liver and kidney function. WB and rt-qPCR analysis confirmed that FHT could inhibit the expression of PIK3CG and the activation of PIK3CG/Akt pathway. Via network pharmacological analysis, molecular docking, and in vivo verification, we demonstrated the multicomponent and multitarget characteristics of FHT in SS treatment, thereby providing novel insights into the pathogenesis of SS and the therapeutic targets of FHT for SS.

A current and future perspective on T cell receptor repertoire profiling

T cell receptors (TCR) play a vital role in the immune system's ability to recognize and respond to foreign antigens, relying on the highly polymorphic rearrangement of TCR genes. The recognition of autologous peptides by adaptive immunity may lead to the development and progression of autoimmune diseases. Understanding the specific TCR involved in this process can provide insights into the autoimmune process. RNA-seq (RNA sequencing) is a valuable tool for studying TCR repertoires by providing a comprehensive and quantitative analysis of the RNA transcripts. With the development of RNA technology, transcriptomic data must provide valuable information to model and predict TCR and antigen interaction and, more importantly, identify or predict neoantigens. This review provides an overview of the application and development of bulk RNA-seq and single-cell (SC) RNA-seq to examine the TCR repertoires. Furthermore, discussed here are bioinformatic tools that can be applied to study the structural biology of peptide/TCR/MHC (major histocompatibility complex) and predict antigenic epitopes using advanced artificial intelligence tools.

Tear miRNAs Identified in a Murine Model of Sjögren’s Syndrome as Potential Diagnostic Biomarkers and Indicators of Disease Mechanism

Objective

The tear miRNAome of the male NOD mouse, a model of ocular symptoms of Sjögren’s syndrome (SS), was analyzed to identify unique miRNAs.

Methods

Male NOD mice, aged 12-14 weeks, were used to identify tear miRNAs associated with development of autoimmune dacryoadenitis. Age- and sex-matched male BALB/c mice served as healthy controls while age-matched female NOD mice that do not develop the autoimmune dacryoadenitis characteristic of SS were used as additional controls. Total RNA was isolated from stimulated tears pooled from 5 mice per sample and tear miRNAs were sequenced and analyzed. Putative miRNA hits were validated in additional mouse cohorts as well as in tears of SS patients versus patients with another form of dry eye disease, meibomian gland disease (MGD) using qRT-PCR. The pathways influenced by the validated hits were identified using Ingenuity Pathway Analysis.

Results

In comparison to tears from both healthy (male BALB/c) and additional control (female NOD) mice, initial analy1sis identified 7 upregulated and 7 downregulated miRNAs in male NOD mouse tears. Of these, 8 were validated by RT-qPCR in tears from additional mouse cohorts. miRNAs previously implicated in SS pathology included mmu-miR-146a/b-5p, which were significantly downregulated, as well as mmu-miR-150-5p and mmu-miR-181a-5p, which were upregulated in male NOD mouse tears. All other validated hits including the upregulated miR-181b-5p and mmu-miR-203-3p, as well as the downregulated mmu-miR-322-5p and mmu-miR-503-5p, represent novel putative indicators of autoimmune dacryoadenitis in SS. When compared to tears from patients with MGD, miRNAs hsa-miR-203a-3p, hsa-miR-181a-5p and hsa-miR-181b-5p were also significantly increased in tears of SS patients.

Conclusions

A panel of differentially expressed miRNAs were identified in tears of male NOD mice, with some preliminary validation in SS patients, including some never previously linked to SS. These may have potential utility as indicators of ocular symptoms of SS; evaluation of the pathways influenced by these dysregulated miRNAs may also provide further insights into SS pathogenesis.

Sex Effects on Gene Expression in Lacrimal Glands of Mouse Models of Sjögren Syndrome

Purpose

Sjögren syndrome is an autoimmune disease that occurs primarily in women, and is associated with lacrimal gland inflammation and aqueous-deficient dry eye. We hypothesize that sex-associated differences in lacrimal gland gene expression are very important in promoting lymphocyte accumulation in this tissue and contribute to the onset, progression, and/or severity of the inflammatory disease process. To test our hypothesis, we explored the nature and extent of sex-related differences in gene expression in autoimmune lacrimal glands.

Methods

Lacrimal glands were collected from age-matched, adult, male and female MRL/MpJ-Tnfrsf6^lpr (MRL/lpr) and nonobese diabetic/LtJ (NOD) mice. Glands were processed for the analysis of differentially expressed mRNAs by using CodeLink Bioarrays and Affymetrix GeneChips. Data were evaluated with bioinformatics and statistical software.

Results

Our results show that sex significantly influences the expression of thousands of genes in lacrimal glands of MRL/lpr and NOD mice. The immune nature of this glandular response is very dependent on the Sjögren syndrome model. Lacrimal glands of female, as compared with male, MRL/lpr mice contain a significant increase in the expression of genes related to inflammatory responses, antigen processing, and chemokine pathways. In contrast, it is the lacrimal tissue of NOD males, and not females, that presents with a significantly greater expression of immune-related genes.

Conclusions

These data support our hypothesis that sex-related differences in gene expression contribute to lacrimal gland disease in Sjögren syndrome. Our findings also suggest that factors in the lacrimal gland microenvironment are critically important in mediating these sex-associated immune effects.

Single-cell analysis reveals sexually dimorphic repertoires of Interferon-γ and IL-17A producing T cells in salivary glands of Sjögren's syndrome mice

The development of Sjögren’s syndrome (SjS) is a dynamic and temporal process with a female predilection. Following the initial influx of immune cells, T cell clusters develop, accelerating the pathology in the salivary glands. Proinflammatory cytokines, IFN-γ and IL-17A, produced by T cells contribute synergistically to the disease. In this study, we examined the sexual dimorphism in cellular infiltrates of the salivary glands by using functional single-cell microengraving analysis. Using high-throughput sequencing, we investigated the clonal diversity of the T cell receptors (TCRs) of infiltrating IFN-γ and IL-17A-producing T cells in male and female SjS-susceptible (SjS^s) C57BL/6.NOD-Aec1Aec2 mice. There were elevated frequencies of IFN-γ and IL-17A-producing effector T cell populations in female SjS^S mice compared to male SjS^S mice. MEME analysis shows high frequency and unique, sexually dimorphic motifs in the TCR hypervariable regions in the SjS^S mice. Male mice selected for TRAV8/TRAJ52 (CATDLNTGANTGKLTFG) TCR genes in Th1 cells and TRBV16/(TRBD1/2)TRBJ1-7 (CGGKRRLESIFR) in Th1 and Th17 cells. Female SjS^S mice selected for TRAV8/TRAJ52 (CATDLNTGANTGKLTFG), TRAV13D-2/TRAJ23 (CVYLEHHFE), and TRBV23/(TRBD2)TRBJ2-2 (CRKLHSCATCALNFL) in Th1 cells. These findings suggest that there is an elevated prevalence of pathogenic effector T cells in the glands with a sexually dimorphic selection bias of TCR repertoires.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

CD8 T cells contribute to lacrimal gland pathology in the nonobese diabetic mouse model of Sjögren syndrome

Sjögren syndrome is an autoimmune disease characterized by targeted destruction of the lacrimal and salivary glands resulting in symptoms of severe ocular and oral dryness. Despite its prevalence, the mechanisms driving autoimmune manifestations are unclear. In patients and in the nonobese diabetic (NOD) mouse model of Sjögren syndrome, lymphocytic infiltrates consist of CD4 and CD8 T cells, although the role of CD8 T cells in disease pathogenesis has been largely unexplored. Here, we evaluated the contribution of CD8 T cells to lacrimal and salivary gland autoimmunity. Within the lacrimal and salivary glands of NOD mice, CD8 T cells were proliferating, expressed an activated phenotype, and produced inflammatory cytokines. Transfer of purified CD8 T cells isolated from the cervical lymph nodes (LNs) of NOD mice into NOD-severe combined immunodeficiency recipients resulted in inflammation of the lacrimal glands, but was not sufficient to cause inflammation of the salivary glands. Lacrimal gland-infiltrating CD8 T cells displayed a cytotoxic phenotype, and epithelial cell damage in the lacrimal glands was observed in recipients of CD8 T cells regardless of the presence of CD4 T cells. Collectively, our results demonstrate that CD8 T cells have a pathogenic role in lacrimal gland autoimmunity. The gland-specific pathogenicity of CD8 T cells makes them a valuable resource to further understand the mechanisms that discriminate lacrimal versus salivary gland autoimmunity and for the development of new therapeutics that target the early stages of disease.

Sjögren syndrome: what and where are we looking for?

PURPOSE OF REVIEW

Sjögren's syndrome affects exocrine glands leading to a dry mouth and dry eyes. Dry eye manifestations can precede the diagnosis of Sjögren's syndrome by many years. Innumerous spontaneous and inducible Sjögren's syndrome models have been used to study the pathogenesis of Sjögren's syndrome. This review focuses on recent human data, ocular and extraglandular manifestations of animal models, what is known, what is still unknown and how we need to look, and their correlation correspondence to human disease.

RECENT FINDINGS

Hallmarks of dry eye in Sjögren's syndrome include increased corneal staining, goblet cell loss and low tear volume. Confocal microscopy and impression cytology are able to clarify new markers of the ocular disease. Extraglandular manifestations should be an alert more severe complications in the eye. Some models have strong sex and exocrine gland predilection, whereas aging generally worsens the disease phenotype. Although most models do not display a significant increase in corneal staining or tear secretion impairment, conjunctival infiltration and decrease in goblet cells are frequently seen.

SUMMARY

We have seen great advances in the role of inflammation in ocular, oral and extra-glandular manifestations of Sjögren's syndrome. Several mechanisms and mediators of Sjögren's syndrome have been elucidated in animal model studies.

Non-proliferating plasma cells detected in the salivary glands and bone marrow of autoimmune NOD.B10.H2b mice, a model for primary Sjögren's syndrome

Autoantibody secreting plasma cells (PCs) are essential contributors in the development of autoimmune conditions such as primary Sjögren's syndrome (pSS). Particularly, the long-lived PC subset residing in the bone marrow has shown to continuously produce autoantibodies, whilst remaining unaffected by immunosuppressive treatment. We have previously shown accumulation of potentially long-lived PCs in chronically inflamed salivary glands of pSS patients. In this study, we aimed to characterise the PC compartment in the salivary glands (the target organ for pSS) and bone marrow before the onset of the murine pSS like disease versus advanced diseases progression. Bromodeoxyuridine (BrdU) was incorporated to distinguish the long-lived PCs. Double immunohistochemical staining and immunofluorescence were then conducted on submandibular gland and bone marrow sections from 8- and 40-week-old mice to identify BrdU and CD138. BrdU(+) cells were detected in the submandibular glands of 8-week-old mice, and observed within all focal infiltrates by 40 weeks of age. Most CD138(+) PCs were however BrdU(-) and located predominantly on the periphery of these infiltrates. This observation was verified through immunofluorescence. A comparable staining pattern was observed in the bone marrow of 8- and 40-week-old NOD.B10.H2b mice, where some of the CD138(+) cells also expressed BrdU. Interestingly, megakaryocytes in the bone marrow of NOD.B10.H2b mice were detected in close proximity to CD138(+) cells, illustrating a possible presence of PC survival niches. Our results demonstrate the presence and accumulation of potentially long-lived PCs in NOD.B10.H2b mice as the disease advances.

Reversible lacrimal gland-protective regulatory T-cell dysfunction underlies male-specific autoimmune dacryoadenitis in the non-obese diabetic mouse model of Sjögren syndrome

CD4(+) CD25(+) Foxp3(+) regulatory T (Treg) cells are required to maintain immunological tolerance; however, defects in specific organ-protective Treg cell functions have not been demonstrated in organ-specific autoimmunity. Non-obese diabetic (NOD) mice spontaneously develop lacrimal and salivary gland autoimmunity and are a well-characterized model of Sjögren syndrome. Lacrimal gland disease in NOD mice is male-specific, but the role of Treg cells in this sex-specificity is not known. This study aimed to determine if male-specific autoimmune dacryoadenitis in the NOD mouse model of Sjögren syndrome is the result of lacrimal gland-protective Treg cell dysfunction. An adoptive transfer model of Sjögren syndrome was developed by transferring cells from the lacrimal gland-draining cervical lymph nodes of NOD mice to lymphocyte-deficient NOD-SCID mice. Transfer of bulk cervical lymph node cells modelled the male-specific dacryoadenitis that spontaneously develops in NOD mice. Female to female transfers resulted in dacryoadenitis if the CD4(+) CD25(+) Treg-enriched population was depleted before transfer; however, male to male transfers resulted in comparable dacryoadenitis regardless of the presence or absence of Treg cells within the donor cell population. Hormone manipulation studies suggested that this Treg cell dysfunction was mediated at least in part by androgens. Surprisingly, male Treg cells were capable of preventing the transfer of dacryoadenitis to female recipients. These data suggest that male-specific factors promote reversible dysfunction of lacrimal gland-protective Treg cells and, to our knowledge, form the first evidence for reversible organ-protective Treg cell dysfunction in organ-specific autoimmunity.

Reduction of T cell receptor diversity in NOD mice prevents development of type 1 diabetes but not Sjögren's syndrome

Non-obese diabetic (NOD) mice are well-established models of independently developing spontaneous autoimmune diseases, Sjögren’s syndrome (SS) and type 1 diabetes (T1D). The key determining factor for T1D is the strong association with particular MHCII molecule and recognition by diabetogenic T cell receptor (TCR) of an insulin peptide presented in the context of I-A^g7 molecule. For SS the association with MHCII polymorphism is weaker and TCR diversity involved in the onset of the autoimmune phase of SS remains poorly understood. To compare the impact of TCR diversity reduction on the development of both diseases we generated two lines of TCR transgenic NOD mice. One line expresses transgenic TCRβ chain originated from a pathogenically irrelevant TCR, and the second line additionally expresses transgenic TCRα^mini locus. Analysis of TCR sequences on NOD background reveals lower TCR diversity on Treg cells not only in the thymus, but also in the periphery. This reduction in diversity does not affect conventional CD4⁺ T cells, as compared to the TCR^mini repertoire on B6 background. Interestingly, neither transgenic TCRβ nor TCR^mini mice develop diabetes, which we show is due to lack of insulin B:9–23 specific T cells in the periphery. Conversely SS develops in both lines, with full glandular infiltration, production of autoantibodies and hyposalivation. It shows that SS development is not as sensitive to limited availability of TCR specificities as T1D, which suggests wider range of possible TCR/peptide/MHC interactions driving autoimmunity in SS.

EBV and other viruses as triggers of tertiary lymphoid structures in primary Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease that targets salivary (SG) and lachrymal glands, leading to exocrine dysfunction. Several viruses have been associated with SS, although the role of persistent viral infections in triggering and/or perpetuating the disease is still a matter of controversy. Together with exocrine dysfunction, SS is characterised by the production of autoantibodies and the presence of lymphomonocytic periductal aggregates in the SG, which in 30/40% of the patients display features of tertiary lymphoid structures (TLS) supporting an ectopic germinal centre response. Here we first review i) the relevance of TLS in SS and ii) the evidence in support of a role for viruses in SS insurgence and/or persistence; next, iii) we review recent data which links viral infection with TLS formation in the SG and suggests that viral-host interactions within TLS favour breach of tolerance and development of autoimmunity in SS.

The important role of T cells and receptor expression in Sjögren's syndrome

Sjögren's syndrome (SjS), an autoimmune disease characterized by exocrine gland dysfunction leading to dry mouth and dry eye diseases, is typified by progressive leucocyte infiltrations of the salivary and lacrimal glands. Histologically, these leucocyte infiltrations generally establish periductal aggregates, referred to as lymphocytic foci (LF), which occasionally appear as germinal centre (GC)-like structures. The formation and organization of these LF suggest an important and dynamic role for helper T cells (TH), specifically TH1, TH2 and the recently discovered TH17, in development and onset of clinical SjS, considered a B cell-mediated hypersensitivity type 2 disease. Despite an ever-increasing focus on identifying the underlying aetiology of SjS, defining factors that initiate this autoimmune disease remain a mystery. Thus, determining interactions between infiltrating TH cells and exocrine gland tissue (auto-)antigens represents a fertile research endeavour. This review discusses pathological functions of TH cells in SjS, the current status of TH cell receptor gene rearrangements associated with human and mouse models of SjS and potential future prospects for identifying receptor-autoantigen interactions.

STIM1 and STIM2 protein deficiency in T lymphocytes underlies development of the exocrine gland autoimmune disease, Sjogren's syndrome

Primary Sjögren's Syndrome (pSS) is an autoimmune disease involving salivary and other exocrine glands that leads to progressive lymphocytic infiltration into the gland, tissue damage, and secretory defects. The mechanism underlying this disease remains poorly understood. Here we report that mice with T-cell-targeted deletion of Stromal Interaction Molecule (STIM) 1 and STIM2 [double-knockout (DKO)] mice develop spontaneous and severe pSS-like autoimmune disease, displaying major hallmarks of the disease. In DKO mice, diffuse lymphocytic infiltration was seen in submandibular glands, a major target of pSS, by age 6 wk, progressing to severe inflammation by age 12 wk. Sjögren's syndrome-specific autoantibodies (SSA/Ro and SSB/La) were detected in the serum, and progressive salivary gland destruction and loss of fluid secretion were also seen. Importantly, we report that peripheral blood mononuclear cells as well as lymphocytic infiltrates in submandibular glands from patients with pSS demonstrated significant reductions in STIM1 and STIM2 proteins. Store-operated calcium entry was also reduced in peripheral blood mononuclear cells from pSS patients compared with those from healthy controls. Thus, deficiency of STIM1 and STIM2 proteins in T cells, and consequent defects in Ca(2+) signaling, are associated with salivary gland autoimmunopathy in DKO mice and pSS patients. These data reveal a previously unreported link between STIM1 and STIM2 proteins and pSS.

TACI-Fc gene therapy improves autoimmune sialadenitis but not salivary gland function in non-obese diabetic mice

OBJECTIVE

Patients with Sjögren's syndrome (SS) show aberrant expression of the B cell-related mediators, B cell-activating factor (BAFF), and a proliferation-inducing ligand (APRIL) in serum and salivary glands (SGs). We studied the biological effect of neutralizing these cytokines by local gene transfer of the common receptor transmembrane activator and CAML interactor (TACI) in an animal model of SS.

MATERIAL AND METHODS

A recombinant serotype 2 adeno-associated virus (rAAV2) encoding TACI-Fc was constructed, and its efficacy was tested in the SGs of non-obese diabetic mice. Ten weeks later, SG inflammation was evaluated and serum and SG tissue were analyzed for inflammatory markers including immunoglobulins (Ig) and cytokines.

RESULTS

AAV2-TACI-Fc gene therapy significantly reduced the number of inflammatory foci in the SG, owing to a decrease in IgD(+) cells and CD138(+) cells. Moreover, IgG and IgM levels, but not IgA levels, were reduced in the SG. Overall expression of mainly proinflammatory cytokines tended to be lower in AAV2-TACI-Fc-treated mice. Salivary flow was unaffected.

CONCLUSION

Although local expression of soluble TACI-Fc reduced inflammation and immunoglobulin levels in the SG, further research will have to prove whether dual blockade of APRIL and BAFF by TACI-Fc can provide a satisfying treatment for the clinical symptoms of patients.

Temporal changes in salivary glands of non-obese diabetic mice as a model for Sjögren's syndrome

OBJECTIVE

Non-obese diabetic (NOD) mice develop an autoimmune exocrinopathy that shows similarities with Sjögren's syndrome. They provide an experimental model to study the pathoetiogenesis of this disease.

MATERIALS AND METHODS

Salivary gland (SG) function and salivary sodium content were measured in 8-, 12-, 16- and 20-week-old NOD and age-matched CB6 mice. In NOD mice, SG expression of phenotypic cell markers, B cell-stimulating and costimulatory molecules were evaluated. Cytokine levels were measured in serum and SG homogenates.

RESULTS

  Microscopically evident SG inflammation in NOD mice was preceded by expression of intercellular adhesion molecule 1 on epithelial cells in the presence of macrophages and relatively high levels of cytokines. Next, an influx consisting of mainly T, B, natural killer, plasma and dendritic cells was seen. Most cytokines, except for interleukin (IL)12/IL23p40 and B cell-activating factor, decreased or remained stable over time, while glandular function deteriorated from 16 weeks of age onward compared with CB6 mice.

CONCLUSION

Sjögren's syndrome-like disease in NOD mice occurs in multiple stages; immunological and physiological abnormalities can be detected before focal inflammation appears and salivary output declines. Extrapolating this knowledge to human subjects could help in understanding the pathogenesis and aid the identification of potential therapeutic targets.

Distinct phenotypes of plasma cells in spleen and bone marrow of autoimmune NOD.B10.H2b mice

Long-lived plasma cells (PCs) residing in the bone marrow (BM) are important producers of protective antibodies. However, when reacting against self-antigens, these PCs produce autoantibodies that contribute to progression of autoimmune diseases such as Sjögren's syndrome (SS). By using a murine model of primary SS, the NOD.B10.H2b mice, we characterized phenotype and generation of PCs at different stages of the pSS disease progression. In general, the PC population found in the NOD.B10.H2b mice expressed high amounts of MHCII, IgG, and BrdU. We further demonstrate the presence of both short- and long-lived PCs in autoimmune spleen and in autoimmune BM. A long-lived PC subset was also found in the spleen and BM of non-autoimmune BALB/c mice, which have not been treated with any immunological agent. Quantitative investigation of splenic and BM PCs revealed that in the NOD.B10.H2 mice, splenic PCs migrate not only to the BM but possibly also to the sites of inflammation. Finally, BM in the aged NOD.B10.H2b mice (40-week-old) presented significantly higher quantities of long-lived PCs than BM of BALB/c mice.

Non-depleting Anti-CD4 Antibody not only Prevents Onset but Resolves Sialadenitis in NOD Mice

The non-obese diabetic (NOD) mouse spontaneously develops lymphocytic infiltrates in the salivary glands (sialadenitis) and provides an useful rodent model of human Sjogren's syndrome (SS). Non-depleting anti-CD4 antibodies have been shown to ameliorate Type 1 diabetes in NOD mice and also vasculitis in MRL/lpr mice. This study shows that a short course of treatment with the non-depleting anti-CD4 monoclonal antibody, YTS 177, completely prevents salivary infiltration and reverses ongoing pathology in the salivary gland.

Are individuals with an autoimmune disease at higher risk of a second autoimmune disorder?

Limited evidence suggests that autoimmune diseases tend to co-occur, although data are needed to determine whether individuals with an existing autoimmune disorder are at increased risk of a second disorder. The authors conducted a series of population-based cohort studies, utilizing the United Kingdom General Practice Research Database, to assess intraindividual risks of coexistence of rheumatoid arthritis (RA), autoimmune thyroiditis (AIT), multiple sclerosis (MS), and insulin-dependent diabetes mellitus (IDDM) during 1990-1999. Sex-specific age- and calendar-period standardized incidence ratios (SIRs) were calculated for development of a second autoimmune disease among index populations including 22,888 RA, 26,198 AIT, 4,332 MS, and 6,170 IDDM patients compared with the general population. Among those with IDDM, adjusted AIT rates were higher than expected for both males (SIR = 646.0, 95% confidence interval (CI): 466, 873) and females (SIR = 409.6, 95% CI: 343, 485), as were RA rates for females (SIR = 181.6, 95% CI: 136, 238). Coexistence of AIT and RA was also shown for either disease sequence (sex-specific SIRs = 130.4-162.0). However, point estimates suggested an inverse relation between RA and MS, irrespective of diagnostic sequence. This study demonstrates coexistence of RA, AIT, and IDDM at higher than expected rates but reduced comorbidity between RA and MS.

Selecting highly sensitive non-obese diabetic mice for improving the study of Sjögren's syndrome

BACKGROUND

Non-obese diabetic (NOD) mice are a commonly used murine model for the study of Sjögren's syndrome. However, variations in susceptibility to the disease among the mice has often yielded less stable results. Based on the correlation between the pathological changes and the tear tests, we attempt to establish a simple screening procedure to assure the validity of experimental results by excluding those mice with poor susceptibility to dry eyes.

METHODS

Seventy male NOD mice were recruited. The tear film break-up test (BUT) and the phenol red cotton thread test (CTT) were implemented while the mice were under anesthesia. The mice were divided into four groups (grades 1 to 4) based on their BUT readings, and four similar groups based on CTT measurements. Tear samples in each grade were collected for IL-1beta detection with ELISA. The lacrimal glands and conjunctiva of the mice were used to detect the levels of leucocyte common antigen (LCA). LCA-Positive staining was considered as the "gold standard" in the receiver operating characteristic curve (ROC curve) analysis. C57BL/6 mice were used as wild-type controls.

RESULTS

There were 13 (18.57%), 43 (61.43%), 10 (14.29%) and 4 (5.71%) mice in grades 1, 2, 3 and 4 by BUT test, and 34 (48.57%), 15 (21.43%), 14 (20.00%) and 7 (10.00%) in grades 1, 2, 3 and 4 by CTT test respectively. Fifty-one out of the 70 mice (72.86%) were detected LCA-positive, and they were mainly in grades 1 and 2 of both the BUT and CCT grading systems. ELISA showed significant variances of IL-beta levels among the four groups (p < 0.01), with much lower IL-beta levels in group 3 and 4 when both BUT and CTT were used for grouping. The tear IL-beta level in the wild-type mice was similar to those of the grade 4 mice, using either BUT or CTT for grouping. The ROC curve analysis provided optimal cutting lines, which were 2 seconds in BUT readings and 4 mm/min in CTT measurements respectively.

CONCLUSION

BUT and CTT tests are useful methods in screening high susceptible NOD mice. Cutting lines at BUT < or = 2 seconds and CTT < or = 4 mm/min provide a good balance between the assurance of susceptibility and the maximization of use of NOD mice for the study of Sjögren's syndrome.

Animal models of Sjögren's syndrome

Sjögren's syndrome is an autoimmune, chronic inflammatory disease characterized by focal mononuclear cell infiltration of exocrine tissues, accompanied by loss of secretory function. The pathogenesis of autoimmune diseases is complex and, therefore, difficult to study in vitro. As of today, the role of initiating factors remains obscure, clinical symptoms develop late, and there are no tests for early diagnosis of SS. Hence, the disease is difficult to detect and treat. Animal models may provide insights into the identification of target antigens, narrowing the relevant pathological immune mechanisms, and to study the evolution of tissue pathology. This review summarizes current knowledge on murine strains, both spontaneous and induced models, used to study Sjögren's syndrome. Special attention is paid to the characteristics of different strains regarding their properties to mimic specific aspects or stages of the disease.

Differential tissue targeting of autoimmunity manifestations by autoantigen-associated Y RNAs

OBJECTIVE

To assess the Y RNAs, a family of homologous RNAs that bind to the Ro autoantigen, for the ability to contribute to autoimmune disease by activating RNA-responsive Toll-like receptors (TLRs).

METHODS

Using cell lines expressing or stably transfected with TLR-3, TLR-7, or TLR-8, we determined the patterns of RNA-specific TLR activation by in vitro transcripts of all of the known murine and human Y RNAs. Next, 8-10-week-old female mice were exposed to a single 50-microg subcutaneous injection of mouse Y1 or mouse Y3 RNA, and the effects were observed.

RESULTS

Y RNA family members differed in their TLR reactivities. Both human and mouse Y3 RNAs, but not other human or mouse Y RNAs, prominently induced TLR-3 activation. Although most human and mouse Y RNAs activated TLR-7 efficiently, mouse Y3 RNA and human Y5 RNA did not. Single subcutaneous injections of mice with either mouse Y1 RNA or mouse Y3 RNA induced or inhibited lymphoid infiltrates in different target organs based on the Y RNA and TLR status of the mouse used. Mouse Y1 RNA induced kidney lesions in TLR-3-intact mice but not in TLR-3-knockout mice. In contrast, mouse Y3 RNA treatment was associated with nephritis in TLR-3-knockout mice but not in TLR-3-intact mice. Sialoadenitis developed in untreated TLR-3-/- mice and in TLR-3-/- mice treated with mouse Y3 RNA, but sialoadenitis was not present in TLR--/-) mice treated with mouse Y1 RNA.

CONCLUSION

Y RNAs can induce innate immune responses and influence clinical manifestations of autoimmunity, suggesting that they are relevant to syndromes of anti-Ro autoimmunity. Distinct patterns of tissue targeting can be seen after exposure to different Y RNAs, in a pattern that correlates with the innate immune signals they induce. Thus, the balance of innate immune signals induced by exposure to endogenous Y RNAs may help determine the nature of the clinical syndrome in anti-Ro autoimmunity.

Identification of nuclear spliceosomal antigens targeted by NOD mouse antibodies following sodium iodide intake

The non-obese diabetic (NOD) mouse spontaneously develops a range of autoreactive responses including an autoantibody response to nuclear antigens. As elevated dietary iodine has been shown to increase thyroid autoimmune pathology in NOD mice, the effect of sodium iodide (NaI) on the development of anti-nuclear antibodies (ANA) was assessed. Interestingly, the NaI symporter is expressed in both thyroid and salivary glands. Elevated dietary iodine was found to increase the percentage of male NOD mice developing autoantibodies. Specifically, the nuclear autoantibodies that develop in NOD mice were shown to target specific spliceosomal components. The target specificity of the autoantibodies was determined using recombinant spliceosomal proteins and shown to include U1A, U170K, U2B'', U2A', as well as the Sm proteins D1, D2, and B. The autoantibody isotypes most consistently represented were IgG2a and IgG2b.

Autoimmune diseases co-occurring within individuals and within families: a systematic review

BACKGROUND

Autoimmune diseases have been observed to coexist both within individuals and within families. It is unclear whether clinical reports of comorbid autoimmune diseases represent chance findings or true associations. This systematic review evaluates the current level of evidence on the coexistence of selected autoimmune diseases within individuals and families. We reviewed the associations among 4 TH1-associated autoimmune diseases: insulin-dependent diabetes mellitus, autoimmune (Hashimoto) thyroiditis, rheumatoid arthritis, and multiple sclerosis.

METHODS

Studies quantifying the coexistence between the selected diseases, published through March 2004, were identified from Medline and Embase searches. Study eligibility was determined on the basis of preestablished criteria, and relevant data were extracted according to a fixed protocol. We determined the prevalence of comorbid autoimmune disease according to index disease and then compiled summary statistics. Heterogeneity among studies was assessed by exact likelihood ratio tests and Monte Carlo inference.

RESULTS

We found 54 studies that met the eligibility criteria. Of these, 52 studies examined the coexistence of disease within individuals and 9 studies examined within-family associations. The majority of studies were uncontrolled and did not account for confounding factors. There was substantial evidence for heterogeneity among studies. Although inconclusive, the data appear to support an increased prevalence of autoimmune thyroiditis among patients with rheumatoid arthritis and those with insulin-dependent diabetes mellitus, and an inverse association between rheumatoid arthritis and multiple sclerosis.

CONCLUSION

Although the available evidence does not permit firm conclusions regarding comorbidities among the selected autoimmune diseases, results are sufficiently suggestive to warrant further study.

Influence on Spontaneous Tissue Inflammation by the Major Histocompatibility Complex Region in the Nonobese Diabetic Mouse

We investigated the role of the major histocompatibility complex (MHC) region in the specificity of autoimmunity by analysing specifically the development of sialadenitis, but also insulitis, nephritis and autoantibody production in autoimmune-prone nonobese diabetic (NOD) mice where the MHC H2g7 haplotype had been exchanged for the H2q (NOD.Q) or H2p (NOD.P) haplotype. The exchange of H2 haplotype did not affect the frequency of sialadenitis because the H2q and H2p congenic NOD strains developed sialadenitis with the same incidence as NOD. However, the severity of sialadenitis varied among the strains, as NOD.Q >NOD >NOD.P. At 11-13 weeks of age, the NOD.Q (H2q) female mice developed more severe sialadenitis compared to NOD.P (H2p) (P=0.038). At 20 weeks, the NOD (H2g7) female mice showed more severe sialadenitis than NOD.P (P=0.049). This is in contrast to the development of insulitis in the present strains, because the incidence of insulitis was almost completely inhibited by the replacement of the H2g7 haplotype of NOD. The incidence of insulitis in NOD.Q was 11-22%, compared to 75% in NOD, which correlated well with lower titres of anti-glutamic acid decarboxylase (anti-GAD) antibodies in NOD.Q compared to NOD (P=0.009). However, the introduction of the H2q haplotype into the NOD strain instead directed the autoimmune response towards the production of lupus types of autoantibodies, because the incidence of antinuclear antibodies (ANA) in NOD.Q was 89% compared with 11% in NOD.P and 12% in NOD mice, which in turn correlated with a high incidence of nephritis in NOD.Q compared to NOD. Consequently, we show that different haplotypes of MHC are instrumental in directing the specificity of the spontaneous autoimmune inflammation.

A T cell intrinsic role of Id3 in a mouse model for primary Sjogren's syndrome

Sjogren's syndrome is an autoimmune disease with clinical hallmarks of keratoconjunctivitis sicca (dry eyes) and xerostomia (dry mouth). The genetic basis of this autoimmune disease is poorly understood. Id3 is an immediate early-response gene in growth regulation and is involved in TCR-mediated T cell selection during T cell development. Here, we show that Id3-deficient mice develop many disease symptoms found in primary Sjogren's syndrome patients including dry eyes and mouth, lymphocyte infiltration in lachrymal and salivary glands, and development of anti-Ro and anti-La antibodies. Adoptive transfer experiment indicated a T cell intrinsic role for Id3 in the development of Sjogren's symptoms. Furthermore, genetic ablation of T cells or neonatal 3 day thymectomy in Id3-deficient mice showed a rescue of disease symptoms, suggesting a thymic origin of autoimmune T cells. Thus, this study establishes a critical connection between Id3-mediated T cell development and autoimmune diseases.

Local adeno-associated virus-mediated interleukin 10 gene transfer has disease-modifying effects in a murine model of Sjögren's syndrome

Female nonobese diabetic (NOD) mice develop spontaneous autoimmune sialadenitis and loss of salivary flow, and are a widely used model of Sjögren's syndrome. We examined the feasibility of local salivary gland immunomodulatory gene delivery to alter these sequelae in NOD mice. We constructed recombinant adeno-associated virus (rAAV) vectors encoding either human interleukin 10 (rAAVhIL-10) or beta-galactosidase (rAAVLacZ, control vector). Mice received rAAVhIL-10 or rAAVLacZ by retrograde submandibular ductal instillation either at age 8 weeks (early, before onset of sialadenitis), or at 16 weeks (late, after onset of sialadenitis). As a systemic treatment control, separate mice received intramuscular delivery of rAAVhIL-10 at each time point. Both submandibular and intramuscular delivery of vector led to low circulating levels of hIL-10. After submandibular administration of rAAVhIL-10, salivary flow rates at 20 weeks for both the early and late treatment groups were significantly higher than for both rAAVLacZ-administered and untreated mice. Systemic delivery of rAAVhIL-10 led to improved salivary flow in the late treatment group. Inflammatory infiltrates in submandibular glands, however, were significantly reduced only in mice receiving rAAVhIL-10 locally in the salivary gland compared with mice receiving this vector intramuscularly, or rAAVLacZ or no treatment. In addition, after submandibular rAAVhIL-10 delivery, NOD mice exhibited significantly lower blood glucose, and higher serum insulin, levels than all other groups, indicating some systemic benefit of this treatment. These studies show that expression of hIL-10 by rAAV vectors can have disease-modifying effects in the salivary glands of NOD mice, and suggest that local immunomodulatory gene transfer may be useful for managing the salivary gland pathology in Sjögren's syndrome.

Protein kinase C expression in salivary gland acinar epithelial cells in non-obese diabetic mice, an experimental model for Sjögren's syndrome

We planned to investigate the expression of protein kinase C (PKC) isoforms in acinar epithelial cells of salivary glands in the non-obese diabetic (NOD) mouse to find out if they develop changes of the PKC system like those seen in the human counterpart, i.e. in Sjögren's syndrome. Parotid, submandibular, and sublingual glands from NOD and control BALB/c mice were stained with a panel of monoclonal antibodies directed against conventional (alpha, beta, and gamma), novel (delta, epsilon, and theta), and atypical (lambda and iota) PKC isoforms using the streptavidin/HRP method. Similarly to human labial salivary glands, acinar epithelial cells of the healthy control BALB/c mice contained two of the conventional PKC isoforms, alpha and beta. Acinar and ductal epithelial cells also contained the atypical PKC isoforms lambda and iota. PKC isoforms gamma, delta, epsilon, and theta were not found. NOD mice which displayed focal sialadenitis contained the same conventional and atypical PKC isoforms. The acinar cells in NOD mice, in contrast to the Sjögren's syndrome patients, did not lack PKC alpha or beta. On the contrary, PKC alpha and beta staining was stronger than in the control BALB/c mice. The present results demonstrate that both conventional and atypical PKC isoforms participate in the salivary epithelial cell biology and that there are mouse strain-associated and/or disease state-associated changes in their expression. The lack of PKC alpha and beta isoforms found in Sjögren's syndrome was not reproduced in NOD mice, which discloses one more difference between the human disease and its NOD mouse model.

Immunization with peptides from 60 kDa Ro in diverse mouse strains

Antibodies binding the Ro (or SSA) and La (or SBB) proteins are commonly found in a high proportion of sera from patients with systemic lupus erythematosus or Sjögren's syndrome. The mechanism by which these autoantibodies arise is not known. Others and we have shown that immunization of nonautoimmune-prone mice with short peptides from the Ro ribonucleoprotein particle can induce autoimmunity to 60 kDa Ro and 52 kDa Ro as well as to the 48 kDa La protein after epitope spreading. We have explored the differences in the epitope spreading after 60 kDa Ro peptide immunization in several strains of mice. There is intra- and intermolecular diversification of the immune response after immunization of DBA/2J animals with a monomer peptide representing the residues 480-494 of the 60 kDa Ro protein, but this peptide does not induce epitope spreading when used as the immunogen in either C57Bl/6J or PL/J mice. Similar to previously studied BALB/c mice, DBA/2J mice have antibodies binding many epitopes of 60 kDa Ro, and some sera bind 52 kDa Ro as well as La. These mice have antinuclear antibody in their sera. These data demonstrate that Ro peptide immunization results in different outcomes depending upon the strain of mouse used. Furthermore, these data suggest that genetic variation is important with regard to responding towards short peptide immunization by epitope spreading.

Animal models of autoimmune polyglandular syndrome

Animal models for autoimmune polyglandular syndrome that are either spontaneous or induced by manipulations are presented. In addition, recent cloning of the autoimmune regulator (AIRE) gene responsible for autoimmune polyglandular syndrome type I, and its homologue in mice, Aire, provided the opportunity to study the effect of this gene on autoimmune diseases by producing knockout mice. These animal models make it possible to perform experiments that cannot be performed in humans, which will increase our understanding of the cause and molecular mechanisms of the autoimmune diseases and lead to the development of effective methods for their prevention and intervention.

Two NOD Idd-associated intervals contribute synergistically to the development of autoimmune exocrinopathy (Sjögren's syndrome) on a healthy murine background

OBJECTIVE

The NOD mouse is genetically predisposed to the development of at least 2 autoimmune diseases, autoimmune diabetes and autoimmune exocrinopathy (AEC). More than 19 chromosomal intervals (referred to as Idd regions) that contribute to diabetes susceptibility in the NOD mouse model have been identified, but only 2 chromosomal intervals (associated with Idd3 and Idd5) have been shown to control sialadenitis. In the present study, we bred the Idd3 and Idd5 chromosomal intervals from NOD mice into non-autoimmune C57BL/6 mice to determine if these intervals recreate a Sjögren's syndrome (SS)-like phenotype.

METHODS

C57BL/6.NODc3 mice carrying Idd3 and C57BL/6.NODc1t mice carrying Idd5 were crossed and intercrossed to generate a C57BL/6.NODc3.NODc1t mouse line homozygous for the Idd3 and Idd5 chromosomal intervals on an otherwise disease-resistant genetic background. C57BL/6.NODc3.NODc1t mice were evaluated for biochemical, pathophysiologic, and immunologic markers characteristic of the SS-like phenotype present in the NOD mouse.

RESULTS

C57BL/6.NODc3.NODc1t mice fully manifested the SS-like phenotype of the NOD mouse, including decreased salivary and lacrimal gland secretory flow rates, increased salivary protein content due in part to less fluid, aberrant proteolytic enzyme activity, decline in amylase activity, appearance of autoantibodies to exocrine gland proteins, and glandular lymphocytic focal infiltrates. Loss of secretory function occurred more rapidly in C57BL/6.NODc3.NODc1t mice (by 12 weeks of age) than in NOD mice (by 16 weeks of age). No signs of insulitis or autoimmune (type 1) diabetes were observed in the C57BL/6.NODc3.NODc1t mice.

CONCLUSION

Genes located within the 2 chromosomal intervals Idd3 and Idd5 appear necessary and sufficient for manifestation of AEC. We propose that this murine model of SS-like disease be designated C57BL/6.NOD-Aec1Aec2. Identification of specific genes within the Aec1 and Aec2 genetic regions should help elucidate the mechanism(s) underlying SS-like disease.

Genetic analysis of autoimmune sialadenitis in nonobese diabetic mice: a major susceptibility region on chromosome 1

The nonobese diabetic (NOD) mouse strain provides a good study model for Sjögren's syndrome (SS). The genetic control of SS was investigated in this model using different matings, including a (NOD x C57BL/6 (B6))F(2) cross, a (NOD x NZW)F(2) cross, and ((NOD x B6) x NOD) backcross. Multiple and different loci were detected depending on parent strain combination and sex. Despite significant complexity, two main features were prominent. First, the middle region of chromosome 1 (chr.1) was detected in all crosses. Its effect was most visible in the (NOD x B6)F(2) cross and dominated over that of other loci, including those mapping on chr.8, 9, 10, and 16; the effect of these minor loci was observed only in the absence of the NOD haplotype on chr.1. Most critically, the chr.1 region was sufficient to trigger an SS-like inflammatory infiltrate of salivary glands as shown by the study of a new C57BL/6 congenic strain carrying a restricted segment derived from NOD chr.1. Second, several chromosomal regions were previously associated with NOD autoimmune phenotypes, including Iddm (chr.1, 2, 3, 9, and 17, corresponding to Idd5, Idd13, Idd3, Idd2, and Idd1, respectively), accounting for the strong linkage previously reported between insulitis and sialitis, and autoantibody production (chr.10 and 16, corresponding to Bana2 and Bah2, respectively). Interestingly, only two loci were detected in the (NOD x NZW)F(2) cross, on chr.1 in females and on chr.7 in males, probably because of the latent autoimmune predisposition of the NZW strain. Altogether these findings reflect the complexity and heterogeneity of human SS.

Prospects for gene-based immunopharmacology in salivary glands

The clinical potential of gene transfer is increasing. One likely major application of this emerging biotechnology will be for gene therapeutics, the use of a gene as a drug. Salivary glands provide an unusual but increasingly valuable target site for gene transfer. Studies in animal salivary glands from several laboratories, including our own, have provided proof of this concept. In this review, we provide a background and perspective on possible strategies for gene-based immunopharmacology in salivary glands. We use as a target disease model the autoimmune exocrinopathy Sjögren's syndrome.

Salivary gland cytokine expression in NOD and normal BALB/c mice

The autoimmune diabetes-prone nonobese diabetic (NOD) mouse develops a chronic lymphocytic infiltration of endocrine and exocrine glands. The objectives of this study were to characterize the salivary immune infiltration and cytokine expression of NOD mice and compare these findings to those of normal BALB/c mice. A decline in salivary flow rates in NOD mice began between 8 and 12 weeks of age. At this same time lymphocytic foci are detectable in the salivary glands. Lymphocytic infiltration in the salivary glands of NOD mice increased with age and simultaneously salivary function declined. No lymphocytic infiltration was seen in BALB/c salivary tissues. Messenger RNA expression of several inflammatory cytokines, including interleukin-1beta (IL-1beta), IL-2, IL-10, interferon-gamma, and tumor necrosis factor-alpha was detected in the submandibular glands of both NOD and BALB/c mice by the reverse transcription polymerase chain reaction. IL-4 synthesis was also present in some tissues. Immunohistochemical analysis demonstrated the intense expression of inflammatory cytokines within lymphocytic infiltrates and epithelial cells of all NOD mice. Minimal expression of the same cytokines was detected only occasionally in BALB/c tissues stained in parallel. These results demonstrate cytokine expression in the salivary glands of normal mice and suggest that the overexpression of these inflammatory cytokines is likely involved in the development and progression of the organ-localized autoimmunity in the salivary glands of NOD mice.

Characterization of the changing lymphocyte populations and cytokine expression in the exocrine tissues of autoimmune NOD mice

NOD mice develop chronic lymphocytic invasion of the pancreas, submandibular, and lacrimal glands leading to loss of insulin secretion, salivary flow, and tear production. In this study, we have used flow cytometric analyses and RT-PCR to track glandular lymphocyte populations and cytokine expression spanning the initiation of autoimmune infiltration through the development of widespread autoimmune destruction of the salivary and lacrimal glands of NOD mice. Results demonstrate a predominance of CD4+ to CD8+ lymphocytes and a similar predominance of T-cells versus B-cells in both the submandibular and lacrimal gland infiltrates. A temporal increase in memory (CD3+CD45RBlo) T-cells was also detected; however, naive (CD3+CD45RBhi) T-cell populations as well as a CD3+, CD4-/CD8- double negative population were also present. In addition, a skewing of the TCR Vbeta repertoire toward Vbeta6+ and Vbeta8+ lymphocytes was evident in both glandular infiltrates. Analyses of cytokine mRNA expression in the submandibular glands demonstrated an increase between 12 and 16 wk of age of several proinflammatory cytokines including IL-1beta, IL-6, IL-7, IL-10, IFNgamma, TNFalpha, and inducible Nitric Oxide Synthase (iNOS). IL-4 synthesis was notably absent in both tissues. Cytokine mRNA transcripts detected in lacrimal tissue were similar to those seen in the submandibular glands but appeared both earlier and more intensely. These findings depict the progressive development of autoimmune exocrinopathy and can be used as a foundation to explore the similarities and potential differences in the immunopathogenic lesions of several distinct tissues within the same host.

A novel NOD-derived murine model of primary Sjögren's syndrome

OBJECTIVE

The appearance of autoimmune diabetes prior to autoimmune exocrinopathy in the NOD mouse suggests that it is an excellent model of secondary, but not primary, autoimmune sicca complications. Since the unique major histocompatibility complex (MHC) I-A(g7) expression in NOD mice is essential for the development of insulitis and diabetes in these animals, we investigated exocrine gland function in NOD.B10.H2b mice, which have an MHC congenic to NOD, as a potential model for primary Sjögren's syndrome (SS).

METHODS

Histopathologic manifestations of lymphocytic infiltrates into the pancreas and exocrine tissues were examined by light microscopy. Sera were evaluated for the presence of antinuclear antibodies. Saliva, tears, and gland lysates were evaluated for total volume and protein concentration, the aberrant expression and processing of parotid secretory protein, and cysteine protease activity.

RESULTS

NOD.B10.H2b mice exhibited the exocrine gland lymphocytic infiltration typical of the SS-like disease and dysfunction observed in NOD mice, but without the insulitis and diabetes. These mice additionally expressed elevated levels of cysteine protease activity (a measure of apoptotic activity) and abnormal expression and cleavage of parotid secretory protein in the submandibular tissues.

CONCLUSION

The results of this study suggest that the unique NOD MHC I-A(g7) is not essential for exocrine tissue autoimmunity. Furthermore, the findings indicate that sicca syndrome occurs independently of autoimmune diabetes and that the congenic NOD.B10.H2b mouse represents a novel murine model of primary SS.

Elevated levels of cysteine protease activity in saliva and salivary glands of the nonobese diabetic (NOD) mouse model for Sjögren syndrome

Nonobese diabetic (NOD) mice develop an anti-exocrine gland pathology similar to human Sjögren syndrome. Recently, we demonstrated that NOD-scid mice develop severe loss of submandibular acinar cells with concomitant appearance of abnormal isoforms of salivary proteins suggesting de novo enzymatic cleavage. Because these changes may indicate activation of apoptotic proteases, we examined saliva and salivary tissue for cysteine protease activity. Cysteine protease activities were elevated in saliva and gland lysates from 20-week-old NOD and NOD-scid mice as compared with age- and sex-matched BALB/c or 8-week-old NOD mice. This activity appeared in the submandibular glands, but not in the parotid glands. Western blot analyses using antibodies directed against specific apoptotic proteases (interleukin 1beta converting enzyme, Nedd-2, and Apopain/CPP 32) confirmed these findings. Submandibular glands from NOD-scid mice exhibited the greatest increase in proteolytic activity, indicating that infiltrating leukocytes are not responsible for these changes. Western blot analyses also failed to reveal changes in the levels of cystatins (saliva proteins that inhibit protease activity). Thus, increased cysteine protease activity appears to be directly related to submandibular acinar cell loss in NOD-scid mice involving the apoptotic pathway. Additional protease activity in saliva and gland lysates of older NOD and NOD-scid mice, apparently mutually distinct from cysteine proteases, generated an enzymatically cleaved parotid secretory protein. We suggest, therefore, that proteolytic enzyme activity contributes to loss of exocrine gland tolerance by generating abnormally processed protein constituents.