Immunological mechanism of IgG4-related disease

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.

Spontaneous Regression of a Pulmonary Inflammatory Myofibroblastic Tumor

Inflammatory myofibroblastic tumors are rare benign mesenchymal neoplasms composed of myofibroblastic cells intermixed with an inflammatory infiltrate of cells including plasma cells, lymphocytes, and histiocytes. These tumors are commonly seen in children and are rare in adults. Management of these tumors is challenging due to their unpredictable behavior. Here, we present a rare case of a pulmonary inflammatory myofibroblastic tumor that regressed spontaneously following a minimally invasive computed tomography-guided percutaneous lung biopsy.

Increased IgD and CD27 Double Negative (DN) B cell population in pediatric onset autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic, inflammatory liver disease of unknown aetiology which requires lifelong immunosuppression. Most therapeutic and outcome studies of AIH have been conducted predominantly in Caucasian (European Ancestry, EA) cohorts, with the exclusion of African American (AA) patients due to inadequate sample size. It is known that AA patients have a severe phenotype of autoimmune diseases and demonstrate a poor response to conventional medical therapy. Understanding cellular and molecular pathways which determine AIH severity and progression in AA patients is likely to lead to the discovery of novel, personalised and better tolerated therapies. The aim of the study is to determine the distinct effector B cell phenotypes which contribute to disease severity and progression of AIH in AA children as compared to their EA cohorts. PBMCs were isolated from blood samples collected from patients visiting Children's Healthcare of Atlanta (CHOA) and were grouped into AA, (n = 12), EA, (n = 11) and controls (n = 12) and were processed for flow cytometry. Markers of B cell development, maturation and activation were assessed namely CD19, CD21, IgD, CD27, CD38, CD11c, CD24, CD138. AA children with AIH demonstrated an expansion of CD19 + ve, Activated Naïve (aN), (CD19+ IgD-/CD27- Double Negative (DN2) ([CD19+/IgD-/CD27++CD38++) cells. Plasmablasts were significantly higher along with Signalling Lymphocytic activation molecule F7 (SLAMF7). Unswitched memory [CD19+] IgD+CD27+ (USM) B cells were significantly contracted in AA patients with AIH. B cell phenotyping reveals a distinct profile in AA AIH patients with a major skewing towards the expansion of effector pathways which have been previously characterised in severe SLE in AA patients. These results suggest that the quantification and therapeutic target of B cell pathway could contribute substantially to the clinical approach to AIH especially in the AA population.

Occurrence and role of Tph cells in various renal diseases

A new population of peripheral helper T (Tph) cells has been identified and contributed to various autoimmune diseases. Tph cells can secrete interleukin-21 (IL-21), interferon (IFN) and C-X-C motif chemokine ligand 13 (CXCL13) to moderate renal disease. Moreover, Tph cells can congregate in huge numbers and immerse within inflamed tissue. Compared to Tfh cells, Tph cells express high programmed cell death protein 1 (PD-1), major histocompatibility complex II (MHC-II), C-C chemokine receptor 2 (CCR2) and C-C chemokine receptor 5 (CCR5) but often lack expression of the chemokine receptor C-X-C chemokine receptor 5 (CXCR5). They display features distinct from other T cells, which are uniquely poised to promote responses and antibody production of B cells within pathologically inflamed non-lymphoid tissues and a key feature of Tph cells. In this review, we summarize recent findings on the role of Tph cells in chronic kidney disease, acute kidney injury, kidney transplantation and various renal diseases.

An Evasive Liver Mass in a Human Immunodeficiency Virus (HIV)-Positive Patient

IgG4-related disease (IgG4-RD) is an autoimmune syndrome that is characterized by elevated levels of serum IgG4 and infiltration of various tissue types by IgG4 immunoreactive plasma cells. The IgG4-RD can result in systemic disease and the formation of inflammatory mass lesions, frequently addressed as pseudotumors. While IgG4-RD can manifest in various organs, liver involvement is rare, and because it is an immune-mediated inflammatory process, it is uncommon in patients who are immunocompromised. Furthermore, despite IgG4-RD responding well to immunosuppressive treatment, cases of spontaneous remission are exceedingly rare in the literature. In this report, we present the unique case of a self-resolving IgG4-RD lesion of the liver in a HIV positive patient.

Renal Manifestations of IgG4-Related Disease: A Concise Review

IgG4-related disease (IgG4-RD) is an immune-mediated disorder marked by fibro-inflammatory masses that can infiltrate multiple organ systems. Due to its relatively recent discovery and limited understanding of its pathophysiology, IgG4-related disease may be difficult to recognize and is consequently potentially underdiagnosed. Renal involvement is becoming regarded as one of the key features of this disease. To date, the most well-recognized renal complication of IgG4-related disease is tubulointerstitial nephritis, but membranous glomerulonephritis, renal masses, and retroperitoneal fibrosis have also been reported. This concise review has two objectives. First, it will briefly encapsulate the history, epidemiology, and presentation of IgG4-related disease. Second, it will examine the reported renal manifestations of IgG4-related disease, exploring the relevant histology, imaging, clinical features, and treatment considerations. This synthesis will be highly relevant for nephrologists, rheumatologists, general internists, and renal pathologists to raise awareness and help improve early recognition of IgG4-related kidney disease (IgG4-RKD).

A Rare Case of Retroperitoneal Tumefactive Fibroinflammatory Lesion Related to IgG4-Sclerosing Disease

We present a unique case of a retroperitoneal tumefactive fibroinflammatory lesion related to IgG4-sclerosing disease; it is a rare manifestation of the IgG4-related disease, which usually causes diffuse fibrosis when located in the retroperitoneum, rather than mass-like lesions. A 49-year-old man presented to the emergency department complaining of abdominal pain and vomiting. Subsequent testing with abdominal ultrasound, CT, and MRI revealed a large retroperitoneal mass of unknown origin, heterogenous, with a concentric circles pattern best visualized in MRI. The lesion was resected, and the histological and immunohistochemical studies revealed an IgG4-related tumefactive fibroinflammatory lesion of the retroperitoneum.

Expression of Immunoglobulin G4 in Eosinophilic Esophagitis

Background: Eosinophilic esophagitis (EoE) is a disease that has been subcategorized into two endoscopic phenotypes: inflammatory and fibrostenotic. Moreover, studies have shown a link between EoE and immunoglobulin G4 (IgG4), a subclass of the immunoglobulin G (IgG) antibody. In this study, we aimed to evaluate the relationship between histologic IgG4 expression and endoscopic phenotypes in patients with EoE. Methods: This case-control study included patients diagnosed with EoE (n = 19) and patients with non-obstructive dysphagia without abnormal findings as controls (NOD; n = 12). The EoE group was further divided into three subgroups based on endoscopic phenotype: inflammatory, fibrostenotic, or combined. Retrospective examination of endoscopic findings and pathological slides was performed to analyze IgG4 staining. Results: Histological analysis revealed a significant difference in IgG4 cell count (15.00 vs. 0.58, p = 0.003) and eosinophil cell count (84.67 vs. 0.08, p < 0.001) between the EoE and NOD groups. Symptom manifestation and blood test results were similar across all three endoscopic EoE phenotypes. However, histological analysis revealed a significant difference in IgG4 cell count between the inflammatory, fibrostenotic, and combined phenotypes (4.13 vs. 17.6 vs. 59.7, p = 0.030). Conclusions: IgG4 expression was higher in EoE patients than in those with NOD, the highest being in the combined phenotype subgroup. These findings emphasize the important role of endoscopic and histological examination in diagnosing EoE and the need for further research in this area.

Multimodality Imaging Features of Immunoglobulin G4-related Vessel Involvement

Immunoglobulin 4 (IgG4)-related disease is a chronic immune-mediated fibroinflammatory disorder. Involvement of the vascular system, including large- and medium-sized vessels, is increasingly recognized. The varied appearances of vascular involvement reflect the sequela of chronic inflammation and fibrosis and can include aortitis and periaortitis with resultant complications such as aneurysm formation and dissection. A diagnosis of IgG4-related large vessel involvement should be considered when there is known or suspected IgG4-related disease elsewhere. Other organs that are typically affected in IgG4-related disease include the lacrimal and salivary glands, thyroid, pancreas, biliary tree, lungs, kidneys, and meninges. Diagnosis typically requires careful correlation with clinical, imaging, serum, and pathologic findings. Patients may be managed with corticosteroid therapy or the anti-CD20 monoclonal antibody, rituximab, if needed. The varied clinical presentations and imaging features of large vessel involvement are discussed herein. Keywords: Vascular, Inflammation, Aorta, IgG4-related Vessel Involvement © RSNA, 2024.

Activation of fibroblasts by plasma cells via PDGF/PDGFR signaling in IgG4-related sialadenitis

IgG4-related sialadenitis (IgG4-SA) is one of the IgG4-related disease. The histological features of IgG4-SA include dense lymphoplasmacytic infiltrates and fibrosis. This study aimed to reveal the involvement of plasma cells in the development of fibrosis and the mechanism underlying fibrosis in IgG4-SA. Hematoxylin-eosin staining, Azan staining, silver staining, and immunohistochemistry (IHC) were performed on IgG4-SA and chronic sialadenitis specimens, and theses samples were analyzed by image analysis software. Histological spatial analysis was used to analyze the localization of IHC-positive cells and the distances between these cells. In the IgG4-SA group, many secondary lymphoid follicles with germinal centers were found, and many collagen fibers developed around these germinal centers. Collagen fibers composed mainly of type I collagen was abundant at sites away from secondary lymphoid follicles, and reticular fibers composed of type III collagen was abundant near secondary lymphoid follicles. Many FAP+ fibroblasts and MUM1+ plasma cells were localized near secondary lymphoid follicles. Histological spatial analysis demonstrated that 90.4% of MUM1+ plasma cells accumulated within 20 µm of FAP+ fibroblasts. Multiple immunofluorescence assays revealed that MUM1+ plasma cells expressed platelet-derived growth factor (PDGF) β, and FAP+ fibroblasts expressed PDGF receptor (PDGFR) β and pSTAT3 in IgG4-SA. We have shown that fibrosis is localized around secondary lymphoid follicles and that fibroblasts are activated by plasma cells via PDGF/PDGFR signaling in IgG4-SA.

Single-cell transcriptome analysis and protein profiling reveal broad immune system activation in IgG4-related disease

IgG4-related disease (IgG4-RD) is a systemic autoimmune disease with unclear pathogenesis. We performed single-cell RNA-seq and surface proteome analyses on 61,379 PBMCs from 9 treatment-naive IgG4-RD patients and 7 age- and sex-matched healthy controls. Integrative analyses were performed for altered gene expression in IgG4-RD, and flow cytometry and immunofluorescence were used for validation. We observed expansion of plasmablasts with enhanced protein processing and activation, which correlated with the number of involved organs in IgG4-RD. Increased proportions of CD4+ cytotoxic T lymphocytes (CTLs), CD8+ CTLs-GNLY (granulysin), and γδT cells with enhanced chemotaxis and cytotoxicity but with suppressed inhibitory receptors characterize IgG4-RD. Prominent infiltration of lymphocytes with distinct compositions were found in different organs of IgG4-RD patients. Transcription factors (TFs), including PRDM1/XBP1 and RUNX3, were upregulated in IgG4-RD, promoting the differentiation of plasmablasts and CTLs, respectively. Monocytes in IgG4-RD have stronger expression of genes related to cell adhesion and chemotaxis, which may give rise to profibrotic macrophages in lesions. The gene activation pattern in peripheral immune cells indicated activation of multiple interaction pathways between cell types, in part through chemokines or growth factors and their receptors. Specific upregulation of TFs and expansion of plasmablasts and CTLs may be involved in the pathogenesis of IgG4-RD, and each of these populations are candidate targets for therapeutic interventions in this disease.

Therapeutic Uses of Rituximab and Clinical Features in Immunoglobulin G4-Related Disease: A Systematic Review

This research presents a systematic review focusing on rituximab's therapeutic applications in immunoglobulin G4 (IgG4)-related disease (IgG4-RD), a rare condition characterized by immune-mediated systemic inflammation and tissue fibrosis, as well as the clinical features of IgG4-RD. While the disease commonly affects organs such as the bile ducts, lymph nodes, retroperitoneum, pancreas, and salivary glands, it can potentially involve other organs. This intricacy often leads to diagnostic challenges due to clinical overlaps with cancer, infections, and other autoimmune disorders. The diagnosis of IgG4-RD necessitates a comprehensive approach involving laboratory tests, imaging studies, and clinical assessments. Symptoms can vary, ranging from lymphadenopathy to jaundice, affecting multiple organs. Although elevated blood IgG4 levels and findings of tissue involvement and fibrosis on imaging can be suggestive, they lack the specificity for a definitive diagnosis. Early diagnosis is crucial for initiating corticosteroids and immunosuppressive to prevent further damage from IgG4-RD. This study highlights the therapeutic role of rituximab in managing this condition. Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria, the research identifies and evaluates relevant literature across various electronic databases, including PubMed, ScienceDirect, and Google Scholar. This review includes 14 selected publications, comprising three systematic reviews, three observational studies, four narrative reviews, and four case reports. The study design ensures a comprehensive evaluation of rituximab's potential efficacy in treating IgG4-RD and its associated clinical characteristics. Based on this study, it can be concluded that IgG4-RD can potentially be treated with rituximab, particularly in cases of relapse and maintaining remission.

Potential impact of autoimmune diseases family history in IgG4-related disease: a retrospective cohort study

OBJECTIVE

Autoimmune comorbidities may be associated with IgG4-related disease (IgG4-RD), here we aimed to determine the correlation of autoimmune diseases (AID) family history and IgG4-RD in a Chinese cohort.

METHODS

This retrospective cohort study identified 628 cases of IgG4-RD in Peking Union Medical College Hospital. Patients were classified into two groups, with AID family history group (AID-positive) and without AID family history group (AID-negative). We viewed the potential value of AID family history on IgG4-RD by comparing the differences between the two groups. In addition, Cox regression analysis estimated CIs and HR for IgG4-RD risk.

RESULTS

93 (14.8%) IgG4-RD patients had AID family history. Compared with AID-negative group, baseline data analysis revealed that AID-positive group patients had an earlier age of IgG4-RD onset (50.4±14.8 vs 54.2±12.6, p=0.014*), a higher percentage of antinuclear antibody (ANA) positivity (38.9% vs 22.7%, p=0.0277*) and Riedel thyroiditis (10.9% vs 2.4%, p=0.001*), were prone to comorbid with other AID (16.1% vs 6.2%, p=0.0238*). Cox analysis found that younger age (HR 0.97 (95% CI 0.94 to 0.99), p=0.0384*) and higher proportions of baseline peripheral eosinophils (HR 1.1 (95% CI 1.02 to 1.2), p=0.0199*) increased the risk of unfavourable prognosis for AID-positive IgG4-RD patients.

CONCLUSIONS

14.8% of IgG4-RD patients had AID family history, with younger age of disease onset age and higher frequency of ANA positivity in AID-positive group, indicating that IgG4-RD may share genetic background with other AID.

Case report: IgG4-related intracranial lesions mimicking multiple sclerosis in a 14-year-old girl

Objectives

IgG4-related disease (IgG4-RD) is distinguished by the infiltration of IgG4-positive plasma cells in a variety of tissues and organs. Even so, central nervous system lesions associated with IgG4-RD are scarce. We present a case of IgG4-related brain parenchymal lesions that mimics multiple sclerosis in a young girl.

Methods

The patient was followed by our neurology and rheumatology teams. Clinical information was recorded, and the brain was screened using magnetic resonance imaging (MRI). During follow-up, we examined serum IgE, IgG and IgG4 and lymph node biopsy.

Results

Here, we presented details of a 14-year-old Chinese girl suffering from diplopia, left eyelid ptosis, right facial numbness, and right lower limb weakness admitted to our institute. Brain MRI revealed multiple sclerosis-like lesions in the brain parenchyma and spinal cord. During the follow-up, she developed lymphadenopathy. Elevation of serum, IgG, IgG4 and IgE and lymph node biopsy favors a diagnosis of IgG4-RD. The patient had a good response to glucocorticoids and mycophenolate mofetil. The literature review summarized eight previously reported IgG4-RD involving brain parenchyma.

Discussion

Our case expands the known age spectrum of IgG4-RD. The intracranial IgG4-RD is rare and could mimic multiple sclerosis. Careful examination and dynamic review of disease history are crucial in the differential diagnosis.

T Cell Roles and Activity in Chronic Sclerosing Sialadenitis as IgG4-Related Disease: Current Concepts in Immunopathogenesis

IgG4-related disease is a multiorgan immunological fibroinflammatory disorder characterized by lymphoplasmacytic infiltration and fibrosis in multiple organs accompanied by high serum IgG4 levels. The salivary glands are the most common organs involved in this disease. Recently, chronic sclerosing sialadenitis affecting salivary glands, formerly known as Küttner's tumor, and Mikulicz's disease have been classified as a class of IgG4-related diseases. The etiopathobiology of IgG4-related disease is not fully understood. It has recently been hypothesized that the inflammatory and fibrotic process and the increased serum IgG4⁺ levels in IgG4-related disease are the result of an interaction between B cells and T helper cells, suggesting that T cells may play a key role in the pathogenesis of this disease. The aim of this review is to discuss the proposed roles of different T cell subsets in the pathogenesis of IgG4-related disease focusing on their roles in immunopathogenesis of IgG4-related sialadenitis.

Optimized Protocols for In-Vitro T-Cell-Dependent and T-Cell-Independent Activation for B-Cell Differentiation Studies Using Limited Cells

Background/Methods

For mechanistic studies, in-vitro human B-cell differentiation and generation of plasma cells are invaluable techniques. However, the heterogeneity of both T-cell-dependent (TD) and T-cell-independent (TI) stimuli and the disparity of culture conditions used in existing protocols make the interpretation of results challenging. The aim of the present study was to achieve the most optimal B-cell differentiation conditions using isolated CD19⁺ B cells and peripheral blood mononuclear cell (PBMC) cultures. We addressed multiple seeding densities, different durations of culturing, and various combinations of TD and TI stimuli including B-cell receptor (BCR) triggering. B-cell expansion, proliferation, and differentiation were analyzed after 6 and 9 days by measuring B-cell proliferation and expansion, plasmablast and plasma cell formation, and immunoglobulin (Ig) secretion. In addition, these conditions were extrapolated using cryopreserved cells and differentiation potential was compared.

Results

This study demonstrates improved differentiation efficiency after 9 days of culturing for both B-cells and PBMC cultures using CD40L and IL-21 as TD stimuli and 6 days for CpG and IL-2 as TI stimuli. We arrived at optimized protocols requiring 2,500 and 25,000 B–cells per culture well for the TD and TI assays, respectively. The results of the PBMC cultures were highly comparable to the B-cell cultures, which allows dismissal of additional B-cell isolation steps prior to culturing. In these optimized TD conditions, the addition of anti-BCR showed a little effect on phenotypic B-cell differentiation; however, it interferes with Ig secretion measurements. The addition of IL-4 to the TD stimuli showed significantly lower Ig secretion. The addition of BAFF to optimized TI conditions showed enhanced B-cell differentiation and Ig secretion in B-cell but not in PBMC cultures. With this approach, efficient B-cell differentiation and Ig secretion were accomplished when starting from fresh or cryopreserved samples.

Conclusion

Our methodology demonstrates optimized TD and TI stimulation protocols for more in-depth analysis of B-cell differentiation in primary human B-cell and PBMC cultures while requiring low amounts of B cells, making them ideally suited for future clinical and research studies on B-cell differentiation of patient samples from different cohorts of B-cell-mediated diseases.

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

Background

A proportion of patients with immunogloblin G (IgG) 4-related disease (IgG4-RD) have hypocomplementemia. We aimed to identify characteristics of such patients.

Methods

We analyzed the demographic and clinical data and complement levels of 85 patients with IgG4-RD. We defined hypocomplementemia as serum C3 and/or C4 levels below the lower limit of normal at diagnosis. We also compared the characteristics of patients with and without IgG4-RD.

Results

Thirty-two (38%) patients had hypocomplementemia at diagnosis. Patients with hypocomplementemia had more lymph node (p < 0.01), lung (p < 0.01), and kidney (p = 0.02) involvement and a higher IgG4-RD responder index than those without (p = 0.05). Additionally, patients with hypocomplementemia had significantly higher IgG (p < 0.01), IgG4 (p < 0.01), and soluble interleukin 2-receptor (sIL-2R) (p < 0.01) levels and total IgG minus IgG4 (p < 0.01). C3 and C4 levels negatively correlated with IgG, IgG4, and sIL-2R levels, total IgG minus IgG4, and number of IgG4-RD responder index: a measure of the disease activity in IgG4-RD. Patients with hypocomplementemia at diagnosis had a significantly higher frequency of relapse (p = 0.024), as determined using the log-rank test. A multivariate logistic regression analysis showed the presence of hypocomplementemia was independently associated with relapse (OR, 6.842; 95% confidence interval [95%CI], 1.684–27.79; p = 0.007).

Conclusions

Patients with IgG4-RD with hypocomplementemia have a more active clinical phenotype, suggesting contributions of the complement system in the pathophysiology of IgG4-RD.

Immunohistochemical analysis of pyroptosis-related protein expression in IgG4-related sialadenitis

Background

NLRP3 (NOD‐, LRR‐ and pyrin domain‐containing protein 3)‐induced pyroptosis is involved in the development of a variety of autoimmune diseases, but its role in IgG4‐related sialadenitis (IgG4‐RS) is unclear.

Methods

Salivary gland tissues from 19 patients with IgG4‐RS were designated the experimental group, and peritumoral tissues from 20 patients with benign salivary gland tumours were designated the control group. The cell morphology and fibrosis in the IgG4‐RS samples were observed by haematoxylin‐eosin (H&E) and Masson trichrome (MT) staining. Immunohistochemical (IHC) staining was used to determine pyroptosis‐related proteins (NLRP3, ASC (apoptosis‐associated speck‐like protein containing a CARD), Caspase‐1, GSDMD (gasdermin family members, including digestive dermatin D), interleukin 1β (IL‐1β), and interleukin 18 (IL‐18)) expression levels.

Results

Increased lymphoid follicle proliferation, germinal centre plasma cell infiltration, and irregular fibrosis were observed in the experimental group compared with the control group. The NLRP3, ASC, Caspase‐1, GSDMD, IL‐1β, and IL‐18 levels were significantly higher in the experimental group than in the control group (p < 0.0001).

Conclusion

This study suggested that pyroptosis‐related proteins might be involved in IgG4‐RS pathogenesis. However, the specific cellular pathway involved and whether multiple cell death pathways contribute to the occurrence of IgG4‐RS still need to be further studied.

The Possible Pathogenic Role of IgG4-Producing Plasmablasts in Stricturing Crohn's Disease

BACKGROUND

Crohn's disease (CD) is a condition on the spectrum of inflammatory bowel disease that affects up to 20 people per 100,000 in the US annually, and with incidence increasing. One of the most significant sources of morbidity in CD is the formation of strictures, with resultant intestinal blockage a common indication for hospitalization and surgical intervention in these patients. The pathophysiology of stricture formation is not fully understood. However, the fibroplasia that leads to fibrostenotic stricture formation may have shared pathophysiology with IgG4-related fibrosis.

SUMMARY

Initial intestinal inflammation recruits innate immune cells, such as neutrophils, that secrete IL-1β and IL-23, which induces a type 17 CD4+ T-helper T-cell (Th17)-mediated adaptive immune response. These CD4+ Th17 T cells also contribute to inflammation by secreting proinflammatory cytokines such as IL-17 and IL-21. IL-21 recruits and stimulates CD4+ T follicular helper (Tfh) cells, which secrete more IL-21. This causes ectopic germinal center formation, recruiting and stimulating naïve B cells. The IL-17 and IL-21 produced by Th17 cells and Tfh cells also induce IgG4 plasmablast differentiation. Finally, these IgG4-producing plasmablasts secrete platelet-derived growth factor (PDGF), which activates local PDGF-receptor expressing fibroblasts and myofibroblasts, resulting in uncontrolled fibroplasia.

IgG4-related autoimmune manifestations in Alemtuzumab-treated multiple sclerosis patients

We aimed to determine whether Alemtuzumab-induced immune reconstitution affects immunoglobulin and complement levels in the serum of Relapsing-Remitting Multiple Sclerosis (RRMS) patients. IgG4-levels were increased 24-months after treatment initiation compared to baseline levels in twenty-nine patients. Alemtuzumab-treated patients with the highest IgG4-levels were more prone to thyroid-related autoimmune manifestations and specific autoimmune adverse events such as Crohn's disease, Graves' disease, and hemolytic anemia. Compared to baseline, total IgG-levels showed a trend towards reduced levels following two-courses of Alemtuzumab, but no significant change of C3 and/or C4-levels was observed. In conclusion, monitoring of IgG4-levels can serve as a marker for secondary autoimmunity risk in multiple sclerosis patients treated with Alemtuzumab.

Autoimmune pancreatitis: What we know so far

Autoimmune pancreatitis (AIP) is a rare, often‐missed disease that involves inflammation of the pancreas and strictures of the pancreatic duct. Its prevalence and incidence in the United States remain scarce. The disease has a varied presentation and often mimics pancreatic malignancy, which can make the diagnosis challenging. Most patients have an excellent response to corticosteroid therapy. Immunomodulators may be used in some cases. Rituximab is an effective, emerging treatment in steroid‐refractory cases. This study aims to review the two distinct types of AIP and provide a detailed analysis of the diagnostic approach and treatment modalities.

Eosinophilic Esophagitis and IgG4: Is There a Relationship?

Our knowledge of the pathophysiology of eosinophilic esophagitis is constantly evolving. There is significant association between eosinophilic esophagitis and atopy; however, multiple studies have refuted the role of IgE in its pathogenesis. Instead, new data have demonstrated an elevated IgG4 level in patients with eosinophilic esophagitis. We review the current understanding of eosinophilic esophagitis pathogenesis and highlight the increasing evidence for the role of IgG4.

Allergic Aspects of IgG4-Related Disease: Implications for Pathogenesis and Therapy

IgG4-related disease (IgG4-RD) is a rare systemic fibroinflammatory disease frequently associated with allergy. The pathogenesis of IgG4-RD is poorly understood, and effective therapies are limited. However, IgG4-RD appears to involve some of the same pathogenic mechanisms observed in allergic disease, such as T helper 2 (Th2) and regulatory T cell (Treg) activation, IgG4 and IgE hypersecretion, and blood/tissue eosinophilia. In addition, IgG4-RD tissue fibrosis appears to involve activation of basophils and mast cells and their release of alarmins and cytokines. In this article, we review allergy-like features of IgG4-RD and highlight targeted therapies for allergy that have potential in treating patients with IgG4-RD.

Hypertrophic Pachymeningitis in a Southern Chinese Population: A Retrospective Study

Aims: To investigate the causes, clinical characteristics, imaging features, and therapeutic implications of hypertrophic pachymeningitis (HP) in a southern Chinese population.

Methods: We retrospectively analyzed 48 patients with HP with different causes from 1 January 2006 to 31 December 2018. Clinical manifestation, laboratory findings, and neuroimaging results were evaluated in all HP patients.

Results: The mean age at onset was 50 ± 12 years. The most common diagnosis was idiopathic HP (67%), followed by antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (15%), tuberculous meningitis (8%), viral meningitis (6%), and bacterial meningitis (4%). Headache was the most common symptom. The most frequently changed laboratory finding was elevated erythrocyte sedimentation rate (ESR). Imaging was characterized by cerebral or spinal dura mater enhancement in MRI scan with contrast. Enhancements were mainly located in the posterior fossa for idiopathic HP; frontal, parietal, and occipital lobes for ANCA-related HP; and posterior fossa for tuberculous-associated HP. Diffuse enhancement was found in most cases, except for tuberculous-associated HP. Glucocorticoid or immunosuppressive treatment was applied in most cases.

Conclusions: The etiology of HP varied among patients, with idiopathic HP being the most common. MRI showed enhancement of the dura mater, which differed according to different etiologies. Glucocorticoid or immunosuppressive agents were the primary drugs for treatment.