Could the complement component C4 or its fragment C4d be a marker of the more severe conditions in patients with primary Sjögren’s syndrome?

Hypocomplementemia in primary Sjogren’s syndrome: association with serological, clinical features, and outcome

Objective

The aim of the present study was to assess the clinical characteristic of hypocomplementemia (HC) in primary Sjogren’s syndrome (pSS), and to address possible risk factors and the prognosis associated with HC in pSS patients.

Methods

pSS patients with HC in Hebei General Hospital from September 2016 to March 2019 were retrospectively analyzed and compared to those with normocomplementemia (NC). Logistic regression analysis was used to detect risk factors.

Results

Of the 333 patients with pSS, 84 patients (25.23%) were presented with HC at diagnosis. The presence of hyper-IgG and anti-Ro52 antibodies was significantly more common in patients with HC. In addition to systemic involvement, pSS patients with HC had more hematological, renal, and nervous system involvement, and received more immunosuppressant treatments than NC group (p < 0.05). ESSDAI score was significantly higher in patients with HC (p < 0.05). Multivariate logistic analysis indicated that leukopenia (OR = 2.23) and hyper-IgG (OR = 2.13) were independent risk factors for pSS with HC. In addition, profound CD16/CD56+ NK-cell lymphopenia was found in pSS-HC patients. More pSS patients developed SLE in the HC group than NC group (4.76% vs. 0.80%, p = 0.04) during the follow-up.

Conclusion

HC was not an uncommon manifestation of pSS and had an independent association with the main clinical and immunological features. Patients with pSS-HC had an increased possibility to develop SLE that required more positive treatment with glucocorticoids and immunosuppressants.

Key Points:

• Hypocomplementemia had an independent association with the main clinical and immunological features in primary Sjogren’s syndrome patients.

• ESSDAI score was significantly higher in patients with hypocomplementemia.

• The pSS patients with hypocomplementemia had an increased possibility to develop SLE.

Meta-Analysis of Autoimmune Regulator-Regulated Genes in Human and Murine Models: A Novel Human Model Provides Insights on the Role of Autoimmune Regulator in Regulating STAT1 and STAT1-Regulated Genes

Autoimmune regulator (AIRE) regulates promiscuous expression of tissue-restricted antigens in medullary epithelial cells (mTEC) of the thymus. To understand the diverse effects of AIRE, it is crucial to elucidate the molecular mechanisms underlying the process of AIRE-regulated gene expression. In this study, we generated a recombinant AIRE expression variant of the TEC 1A3 human cell line, TEC 1A3 AIRE^hi, to determine genes targeted by AIRE, and using microarray analysis, we identified 482 genes showing significant differential expression (P < 0.05; false discovery rate <5%), with 353 upregulated and 129 downregulated by AIRE expression. Microarray data were validated by quantitative PCR, confirming the differential expression of 12 known AIRE-regulated genes. Comparison of AIRE-dependent differential expression in our cell line model with murine datasets identified 447 conserved genes with a number of transcription regulatory interactions, forming several key nodes, including STAT1, which had over 30 interactions with other AIRE-regulated genes. As STAT1 mutations cause dominant chronic mucocutaneous candidiasis and decreased STAT1 levels in monocytes of autoimmune polyglandular syndrome 1 (APS-1) patients, it was important to further characterize AIRE–STAT1 interactions. TEC 1A3AIRE^hi were treated with the STAT1 phosphorylation inhibitors fludarabine and LLL3 showed that phosphorylated STAT1 (p-STAT1) was not responsible for any of the observed differential expression. Moreover, treatment of TEC 1A3 AIRE^hi with STAT1 shRNA did not induce any significant variation in the expression of unphosphorylated STAT1 (U-STAT1) downstream genes, suggesting that these genes were directly regulated by AIRE but not via U-STAT1. The novel model system we have developed provides potential opportunities for further analysis of the pathogenesis of (APS-1) and the wider roles of the AIRE gene.

Distribution of Peripheral Lymphocyte Populations in Primary Sjögren's Syndrome Patients

Purpose of this study was to evaluate the lymphocyte populations' distribution changes in peripheral blood of patients with primary Sjögren's syndrome (pSS). Lymphocyte populations' distribution changes in peripheral blood of pSS patients were investigated in 52 patients with pSS and in 28 healthy controls by flow cytometry. We found decreased absolute count of CD3⁺ T cell population in pSS patients. Analysis of CD4⁺ T cell population showed significant proportion and absolute count differences in pSS patient's blood with SSA/SSB antibodies (Abs) in comparison to controls. No significant differences were observed analyzing CD4⁺ and CD8⁺ Treg subpopulation. Proportion and absolute counts of Th17 cells were significantly lower in pSS patient's blood. Absolute counts of CD8⁺ T cells were significantly lower in pSS patients in comparison to controls and also impaired proportion and absolute counts of CD8⁺ subpopulations according to CD27⁺ and CD57⁺ were observed. Absolute counts of NKT and NK cells were decreased in pSS with Abs. B cells proportion was increased only in blood of pSS with Abs. Lymphocyte distribution impairment can be due to genetically determined lymphopenia or lymphocyte migration from periphery to inflammatory sites or/and increased susceptibility to apoptosis.