Not all autoantibodies are clinically relevant. Classic and novel autoantibodies in Sjögren’s syndrome: A critical review

TLR7/8 Activation in Immune Cells and Muscle by RNA-Containing Immune Complexes: Role in Inflammation and the Pathogenesis of Myositis

OBJECTIVE

Activation of endosomal toll-like receptors (TLRs) is one possible driver of inflammation in idiopathic inflammatory myopathies (IIM). We investigated the potential contribution of TLR7 and TLR8 to IIM pathogenesis.

METHODS

Activation of TLR7/8 in healthy donor peripheral blood mononuclear cells (PBMCs) by immune complexes from patients with IIMs and lupus was tested. Autoantibody profiling of patient IgG samples was performed using a 1581 antigen array. TLR7 and/or TLR8 activation by RNA molecules associated with autoantibodies was assessed. Gene expression in human myoblasts and satellite cells following treatment with supernatants from TLR7/8-activated PBMCs was evaluated by NanoString. C57BL/6 mice were dosed intramuscularly with the TLR7/8 agonist R848 and single-cell RNA-sequencing was performed on the muscle to ascertain the cell types responding to TLR7/8 activation and the downstream effects.

RESULTS

Overall, 69 patients with IIMs were included with representation of dermatomyositis, polymyositis, and inclusion body myositis subsets. Immune complexes from patients with IIMs, as well as autoantibody-associated RNAs histidyl-transfer RNA, Y1, Y4, and U1, activated PBMCs to produce interferon-α and IL-6 via TLR7/8. Several canonical (Ro60, Ro52, and HIST1H4A) and novel (IL-36RN) autoreactivities correlated highly with TLR7/8 activation. Supernatants from TLR7/8-activated PBMCs had a negative impact on human myoblasts and satellite cells. Endothelial cells were activated by R848 in mouse muscle in vivo in addition to immune cells such as monocytes and macrophages.

CONCLUSION

Our results suggest that patients with IIMs have autoantibodies in their blood causing TLR7/8 activation, which leads to inflammation in muscles with potential deleterious effects.

Novel autoantibodies help diagnose anti-SSA antibody negative Sjögren disease and predict abnormal labial salivary gland pathology

OBJECTIVES

Sjögren disease (SjD) diagnosis often requires either positive anti-SSA antibodies or a labial salivary gland biopsy with a positive focus score (FS). One-third of patients with SjD lack anti-SSA antibodies (SSA-), requiring a positive FS for diagnosis. Our objective was to identify novel autoantibodies to diagnose 'seronegative' SjD.

METHODS

IgG binding to a high-density whole human peptidome array was quantified using sera from SSA- SjD cases and matched non-autoimmune controls. We identified the highest bound peptides using empirical Bayesian statistical filters, which we confirmed in an independent cohort comprising SSA- SjD (n=76), sicca-controls without autoimmunity (n=75) and autoimmune-feature controls (SjD features but not meeting SjD criteria; n=41). In this external validation, we used non-parametric methods for binding abundance and controlled false discovery rate in group comparisons. For predictive modelling, we used logistic regression, model selection methods and cross-validation to identify clinical and peptide variables that predict SSA- SjD and FS positivity.

RESULTS

IgG against a peptide from D-aminoacyl-tRNA deacylase (DTD2) bound more in SSA- SjD than sicca-controls (p=0.004) and combined controls (sicca-controls and autoimmune-feature controls combined; p=0.003). IgG against peptides from retroelement silencing factor-1 and DTD2 were bound more in FS-positive than FS-negative participants (p=0.010; p=0.012). A predictive model incorporating clinical variables showed good discrimination between SjD versus control (area under the curve (AUC) 74%) and between FS-positive versus FS-negative (AUC 72%).

CONCLUSION

We present novel autoantibodies in SSA- SjD that have good predictive value for SSA- SjD and FS positivity.

[Clinical characteristics and labial gland pathological features in children with systemic lupus erythematosus complicated by Sjögren's syndrome]

OBJECTIVES

To study the clinical manifestations, laboratory features, and labial gland pathological features in children with systemic lupus erythematosus (SLE) complicated by Sjögren's syndrome (SS).

METHODS

A retrospective analysis was conducted on 102 children with SLE who underwent labial gland biopsies at Renji Hospital, Shanghai Jiao Tong University School of Medicine from January 2013 to December 2022. The children were divided into two groups based on the presence of SS: the SLE with SS group (SLE-SS; 60 children) and the SLE-only group (42 children). According to the focus score (FS) of the labial glands, children in the SLE-SS group were further subdivided into FS≥4 subgroup (26 children) and FS<4 subgroup (34 children). The clinical data of the groups were compared.

RESULTS

Compared to the SLE-only group, children in the SLE-SS group had less skin and mucosal involvement, were more likely to have positive anti-SSA and anti-SSB antibodies, and had higher levels of rheumatoid factor (P<0.05). There was no significant difference in treatment protocols between the two groups (P>0.05). Compared to the FS<4 subgroup, the FS≥4 subgroup had more frequent musculoskeletal involvement (P<0.05), but there was no significant difference in SLE disease activity or other major organ involvement between the subgroups (P>0.05).

CONCLUSIONS

Children with SLE complicated by SS are less likely to have skin and mucous membrane involvement and exhibit specific serological characteristics. The SLE-SS children with an FS≥4 are more likely to experience musculoskeletal involvement. However, FS is not associated with disease activity or other significant organ damage.

Exploring Sjögren's syndrome through interdisciplinary perspectives: a concise review

Dr. Henrik Sjögren after whom Sjögren's Syndrome is named, was a Swedish ophthalmologist who identified the syndrome which had three main symptoms namely, dry eyes, dry mouth, and arthritis. His contributions also highlighted the systemic complications of the syndrome which made our understanding of this disease better. Since then, there have been several studies on Sjögren's Syndrome (SS) of which two of them have changed the perception of the disease's prevalence. The first was a British study in the late 1990s which indicated this syndrome was no more a rare condition. The second is a 2008 study in the US which placed the syndrome as the second most prevalent autoimmune disease after rheumatoid arthritis (RA). Being one of the most prevalent autoimmune disease, there is a pressing need for a more profound and comprehensive understanding of the syndrome. This review endeavors to offer a comprehensive overview of the disease, encompassing its prevalence, manifestations, mechanisms, genetic factors, diagnostic methods, and treatment options. This review additionally offers the āyurvedic viewpoint on SS and its symptoms. This supplementary insight has the potential to contribute to the development of an integrated and holistic approach to managing the condition.

Clinical Profile of Patients with Primary Sjögren's Syndrome with Non-Identified Antinuclear Autoantibodies

Objectives-The aim of the present study was to characterize the clinical phenotype of patients with primary Sjögren's syndrome (pSS) with non-identified antinuclear antibodies (ANA) in comparison with that of patients with pSS with negative ANA, positive typical ANA (anti-Ro/SSA and/or La/SSB) and positive atypical ANA. Methods-We conducted an observational, retrospective monocentric study at the Erasme University Hospital (Brussels, Belgium). Two hundred and thirty-three patients fulfilling the 2002 American-European Consensus Group criteria for pSS were included in this study. The patients were subdivided according to their ANA profile and demographics. The clinical and biological data of each subgroup were compared. Moreover, the relationships between these data and the ANA profiles were determined by multiple correspondence analysis. Results-In our cohort, 42 patients (18%) presented a non-identified ANA-positive profile. No statistically significant difference could be observed between non-identified ANA patients and ANA-negative patients in terms of age and/or ESSDAI score at diagnosis. There were significantly more frequent articular manifestations, positive rheumatoid factor (RF), and the use of corticosteroids in anti-Ro/SSA-positive patients compared to ANA-negative (p ≤ 0.0001) and non-identified ANA-positive patients (p ≤ 0.01). However, a significantly higher proportion of RF positivity and corticosteroid treatment was observed in non-identified ANA-positive patients compared to ANA-negative patients (p < 0.05). Conclusions-For the first time to our knowledge, our study has characterized the clinical phenotype of patients with pSS with non-identified ANA at diagnosis. The non-identified ANA-positive patients featured mostly a clinical phenotype similar to that of the ANA-negative patients. On the other hand, the non-identified ANA-positive patients were mainly distinguished from the ANA-negative patients by a greater proportion of RF positivity and the need for corticosteroid use due to articular involvement.

Human umbilical cord mesenchymal stem cells improve disease characterization of Sjogren's syndrome in NOD mice through regulation of gut microbiota and Treg/Th17 cellular immunity

BACKGROUND

For the unclear pathogenesis of Sjogren's syndrome (SS), further exploration is necessary. Mesenchymal stem cells (MSCs) and derived exosomes (MSCs-exo) have exhibited promising results in treating SS.

OBJECT

This study aimed to investigate the effect and mechanism of human umbilical cord MSCs (UC-MSCs) on SS.

METHODS

Nonobese Diabetic (NOD) mouse splenic T cells were co-cultured with UC-MSCs and UC-MSCs-exo, and interferon-gamma (IFN-γ), interleukin (IL)-6, IL-10, prostaglandin E2 (PGE2), and transforming growth factor-β1 (TGF-β1) levels in the supernatant were assessed by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Co-cultured T cells were injected into NOD mice via the tail vein. The inflammatory cell infiltration in the intestine and the submandibular gland was characterized by hematoxylin-eosin staining. Treg/Th17 homeostasis within the spleen was determined by flow cytometry. Gut microbiota was detected by 16S rRNA sequencing, and the relationship between differential microbiota and Treg/Th17 cytokines was analyzed by the Pearson correlation coefficient.

RESULTS

UC-MSCs, UC-MSCs-exo, and NOD mouse splenic T cells were successfully cultured and identified. After T cells were co-cultured with UC-MSCs and UC-MSCs-exo, both IFN-γ and IL-6 were decreased while IL-10, PGE2, and TGF-β1 were increased in transcriptional and translational levels. UC-MSCs and UC-MSCs-exo partially restored salivary secretion function, reduced Ro/SSA antibody and α-Fodrin immunoglobulin A levels, reduced inflammatory cell infiltration in the intestine and submandibular gland, raised proportion of Treg cells, decreased IFN-γ, IL-6, IL-2, IL-17, lipopolysaccharide, and tumor necrosis factor-alpha levels, and raised IL-10, Foxp3, and TGF-β1 levels by affecting co-cultured T cells. The intervention of UC-MSCs and UC-MSCs-exo improved intestinal homeostasis in NOD mice by increasing microbiota diversity and richness. Additionally, differential microbiota was significantly associated with Treg/Th17 cytokine levels.

CONCLUSION

Human UC-MSCs and UC-MSCs-exo improved disease characterization of SS in NOD mice through regulation of gut microbiota and Treg/Th17 cellular immunity.

Secondary renal amyloidosis due to primary Sjogren's syndrome: a case report

Amyloidosis is a rare disorder characterized by the deposition of abnormal proteins in extracellular tissues, resulting in the dysfunction of vital organs and, eventually, death. The occurrence of amyloidosis due to primary Sjogren's syndrome (pSS) is a rare finding. This study describes a rare case of pSS complicated by amyloid-associated amyloidosis.

Case presentation

A 35-year-old male was diagnosed with nephrotic syndrome and secondary amyloidosis caused by pSS. He had microscopic hematuria, a creatinine level of 6.59 mg/dl, and an elevated erythrocyte sedimentation rate of 107 mm/hrs. Furthermore, investigations of antinuclear antibodies, antimitochondrial antibodies, SSA, SSA native, and Ro-52 recombinant as well as rheumatoid factor showed positive results. After establishing the diagnosis of pSS through clinical, physical, and laboratory assessments, a renal biopsy was performed, which revealed the occurrence of secondary amyloidosis.

Clinical discussion

The risk of developing secondary amyloidosis depends on the extent of elevated serum amyloid levels as well as persistent subclinical inflammation. The definitive diagnosis of amyloidosis requires histological confirmation of amyloid fibril deposition in tissue.

Conclusion

Secondary renal amyloidosis is an unusual condition in patients with pSS. Still, it should be regarded in the differential diagnosis of patients with proteinuria and/or renal failure, and a renal biopsy should be performed.