Clinical Characteristics of Patients With IgG4-Related Disease Complicated by Hypocomplementemia

Anti-PGK1 antibodies in immuno-related pancytopenia

OBJECTIVE

Phosphoglycerate kinase 1 (PGK1) was previously screened as a possible autoantigen for IRP, this study further investigates the value of PGK1 autoantibodies in the diagnosis of IRP and their correlation with other clinical indicators.

METHOD

Anti-PGK1 antibodies were screened in untreated IRP patients and SAA patients by ELISA.CD5 + B cells and BMMNC-Ab were detected in untreated and recovered IRP patients by FCM. Clinical findings were compared between different groups.

RESULT

The serum level of anti-PGK1 antibodies of untreated IRP patients was significantly higher than that of SAA patients; the percentage of PGK1-Ab positive patients was lower in PLT > 50*109/L group in recovered IRP patients and PGK1-Ab levels in the recovered IRP patients were positively correlated with WBC and CIC levels and negatively correlated with PLT levels. PLT was positively correlated with CIC levels in the untreated IRP group. After treatment, the levels of C3 and C4, the percentage of CD34+ IgM positivity, and CD5+ B cells of IRP patients decreased significantly.

CONCLUSION

Detecting anti-PGK1 antibodies might have some clinical value in differentiating IRP from SAA. The tests of CD34+ IgM positivity, CD5+ B cells, and C3 and C4 levels are of clinical value in assessing the curative effect of IRP patients.

IgG-Associated Hypocomplementemia in Neonatal Lupus: A Retrospective Multicenter Study

Background

Hypocomplementemia, defined as a complement C3 or C4 level below the normal lower limit, is strongly associated with an unfavorable prognosis in patients with autoimmune diseases. This study aimed to explore the clinical features and outcomes of patients with neonatal systemic lupus erythematosus (NLE) with hypocomplementemia.

Methods

This retrospective clinical study was conducted across four tertiary hospitals in Eastern China on January 1, 2011, and December 31, 2023. This study included 91 patients with NLE. Patients were classified into hypocomplementemic and non-hypocomplementemic groups according to their serum C3 and/or C4 levels. Risk factors for the development of hypocomplementemia were explored using univariate/multifactorial analyses, organ involvement, and follow-up outcomes were compared between groups.

Results

The number of NLE patients with hypocomplementemia was 36 (39.56%). Hypocomplementemia group had a significantly lower proportion of fish oil supplementation during pregnancy, a higher proportion of cesarean deliveries, mothers with systemic lupus erythematosus, double antibody positivity for anti-SSA and anti-SSB, and higher serum IgG levels. Multivariate analyses showed that maternal allergic diseases, double antibody positivity, and serum IgG levels were risk factors for hypocomplementemia. Baseline IgG levels negatively correlated with complement C3 and C4 levels. NLE Patients with hypocomplementemia are more likely to have thrombocytopenia, hypoproteinemia, or gastrointestinal involvement than those without hypocomplementemia. Systemic application of glucocorticoids was significantly more prevalent in the hypocomplementemia group. Long-term follow-up revealed that allergy-associated disorders were common in patients with NLE and hypocomplementemia, followed by developmental delay, severe infections, attention- deficit hyperactivity disorder, and anxiety/depression, respectively. Log-rank analysis revealed that these patients had significantly higher frequencies of allergic diseases and developmental delays later in life.

Conclusion

Maternal allergic diseases, double antibody positivity, and serum IgG levels were associated with the development of hypocomplementemia in children with NLE. Patients with hypocomplementemia-associated NLE typically exhibit a more severe disease course.

The Differential Complement, Fc and Chemokine Receptor Expression of B Cells in IgG4-Related Pancreatobiliary Disease and Primary Sclerosing Cholangitis and Its Relevance for Targeting B Cell Pathways in Disease

Background: Immune-mediated liver and biliary conditions, such as IgG4-related pancreatobiliary disease (IgG4-PB) and a subset of primary sclerosing cholangitis (PSC- high(h)IgG4), exhibit increased IgG4 levels in the blood. The relative expression of IgG4+ and IgG1+ B cells in the blood and the expression of complement and Fc receptors on these IgG1+ and IgG4+ B cells in IgG4-PB and PSC have not been previously described. We hypothesised that the patterns of expression of these cells and their receptors would differ, are relevant to disease pathogenesis and may represent therapeutic targets. Methods: CD19+ B cells were sorted from blood collected from patients with IgG4-PB, PSC-high(h)IgG4 and healthy volunteers. Cells were stained with fluorescent labelled antibodies specific to IgG1, IgG4, complement receptors (CR1 and CR2), Fc receptors (FcεRII and FcγRIIb) and chemokine receptors (CXCR3, CXCR4, CXCR5) and were analysed by flow cytometry. Findings: IgG4-PB, compared to healthy volunteers, showed decreased CR2 expression on IgG1+ B cells (MFI 416 (275-552) vs. 865 (515-3631), p = 0.04) and IgG4+ B cells (MFI 337 (231-353) vs. 571 (398-2521), p = 0.03). IgG4-PB, compared to healthy volunteers, showed increased FcεRII expression on IgG4+ B cells (MFI 296 (225-617) vs. 100 (92-138), p = 0.0145) and decreased FcγRIIb expression on IgG1+ B cells (134 (72-161) vs. 234 (175-291), p = 0.0262). FcγRIIb expression was also decreased in IgG1+ B cells in patients with PSC-hIgG4 compared to healthy volunteers. Conclusions: This exploratory study indicates that in IgG4-PB, B cells have decreased CR2 and FcγRIIb expression and increased FcεRII expression, suggesting altered sensitivity to complement, IgG-mediated inhibition and sensitisation by IgE, which may promote the relative expansion of IgG4+ B cells in this disease.

Multiorgan involvement and circulating IgG1 predict hypocomplementaemia in IgG4-related disease

OBJECTIVES

Hypocomplementaemia is common in patients with IgG4-related disease (IgG4-RD). We aimed to determine the IgG4-RD features associated with hypocomplementaemia and investigate mechanisms of complement activation in this disease.

METHODS

We performed a single-centre cross-sectional study of 279 patients who fulfilled the IgG4-RD classification criteria, using unadjusted and multivariable-adjusted logistic regression to identify factors associated with hypocomplementaemia.

RESULTS

Hypocomplementaemia was observed in 90 (32%) patients. In the unadjusted model, the number of organs involved (OR 1.42, 95% CI 1.23 to 1.63) and involvement of the lymph nodes (OR 3.87, 95% CI 2.19 to 6.86), lungs (OR 3.81, 95% CI 2.10 to 6.89), pancreas (OR 1.66, 95% CI 1.001 to 2.76), liver (OR 2.73, 95% CI 1.17 to 6.36) and kidneys (OR 2.48, 95% CI 1.47 to 4.18) were each associated with hypocomplementaemia. After adjusting for age, sex and number of organs involved, only lymph node (OR 2.59, 95% CI 1.36 to 4.91) and lung (OR 2.56, 95% CI 1.35 to 4.89) involvement remained associated with hypocomplementaemia while the association with renal involvement was attenuated (OR 1.6, 95% CI 0.92 to 2.98). Fibrotic disease manifestations (OR 0.43, 95% CI 0.21 to 0.87) and lacrimal gland involvement (OR 0.53, 95% CI 0.28 to 0.999) were inversely associated with hypocomplementaemia in the adjusted analysis. Hypocomplementaemia was associated with higher concentrations of all IgG subclasses and IgE (all p<0.05). After adjusting for serum IgG1 and IgG3, only IgG1 but not IgG4 remained strongly associated with hypocomplementaemia.

CONCLUSIONS

Hypocomplementaemia in IgG4-RD is not unique to patients with renal involvement and may reflect the extent of disease. IgG1 independently correlates with hypocomplementaemia in IgG4-RD, but IgG4 does not. Complement activation is likely involved in IgG4-RD pathophysiology.

Performance of classification and diagnostic criteria for IgG4-related disease and comparison of patients with and without IgG4-related disease

IgG4-related disease (IgG4-RD) was recently described in Japan. It is characterised by extensive organ involvement with tissue fibrosis. We assessed the performance of the 2019 American College of Rheumatology and European League Against Rheumatism (ACR/EULAR) classification criteria and the 2020 revised comprehensive diagnostic (RCD) criteria as well as differences between patients with and without IgG4-RD. In this retrospective, single-centre study of 50 patients admitted with suspected IgG4-RD, we evaluated the sensitivity and specificity of both criteria. We also compared clinical characteristics and laboratory data of patients with IgG4-RD (n = 42) and patients without IgG4-RD (n = 8). The ACR/EULAR classification criteria had 88.1% sensitivity and 87.5% specificity for IgG4-RD diagnosis. The RCD criteria had 100% sensitivity and 50% specificity. Patients with IgG4-RD had significantly more affected organs (p = 0.002). Patients with a single affected organ and IgG4-RD had significantly higher serum IgG4/IgG ratios (p = 0.027), lower serum C-reactive protein levels (p = 0.020), and lower total haemolytic complement activity (p = 0.044) than those without IgG4-RD. The ACR/EULAR classification criteria have high specificity and the RCD criteria have high sensitivity for diagnosing IgG4-RD. The number of affected organs is important for diagnosing IgG4-RD.

Correlation between serologic parameters and disease activity of IgG4-related disease: Differences between patients with normal and elevated serum IgG4 concentrations

Objective

We aimed to identify serologic parameters that correlate with the disease activity of IgG4-related disease (IgG4-RD) in patients with normal and elevated serum IgG4 concentrations, respectively.

Methods

This retrospective cohort study included 148 patients with IgG4-RD. Patients were categorized into normal (≤201 mg/dL) and elevated (>201 mg/dL) serum IgG4 concentration groups. Disease activity was assessed using the IgG4-RD responder index (RI). The correlations between IgG4-RD RI and serologic parameters (erythrocyte sedimentation rate [ESR], C-reactive protein, C3, C4, IgG4 concentration, IgG concentration, and IgG4/IgG ratio) were evaluated in each group, using Spearman’s correlation coefficient.

Results

Of the 148 patients with IgG4-RD, 38 (25.7%) and 110 (74.3%) patients were categorized into the normal and elevated serum IgG4 concentration groups, respectively. In the normal serum IgG4 concentration group, IgG concentration was the only serologic parameter that showed a significant correlation with IgG4-RD RI (rho=0.411, p=0.013). However, in the elevated serum IgG4 concentration group, ESR (rho=0.196, p=0.041), C3 (rho=-0.432, p<0.001), C4 (rho=-0.363, p=0.001), IgG4 concentration (rho=0.423, p<0.001), IgG concentration (rho=0.224, p=0.020), and IgG4/IgG ratio (rho=0.328, p=0.001) correlated with IgG4-RD RI. The combination of C3 and IgG4 concentration (rho=0.509, p<0.001) had the strongest correlation with IgG4-RD RI in this group.

Conclusion

Among the serologic parameters tested, IgG concentration was the only parameter that correlated with IgG4-RD RI in patients with normal serum IgG4 concentrations, whereas multiple parameters correlated with IgG4-RD RI in those with elevated serum IgG4 concentrations. The combination of C3 and IgG4 concentration had the strongest correlation coefficient in the latter group.