The Immunologic Paradoxes of IgG4-Related Disease

Single-cell transcriptome analysis profiles cellular and molecular alterations in submandibular gland and blood in IgG4-related disease

OBJECTIVES

The aim of this study is to profile the transcriptional landscapes of affected tissues and peripheral blood mononuclear cells (PBMCs) at the single-cell level in IgG4-related disease (IgG4-RD). Identifying the cell populations and crosstalk between immune cells and non-immune cells will assist us in understanding the aetiology of IgG4-RD.

METHODS

We performed single-cell RNA sequencing analysis on submandibular glands (SMGs) and PBMCs from patients with IgG4-RD and matched controls. Additionally, bulk RNA sequencing of PBMCs was used to construct the immune repertoire. Furthermore, multiplex immunofluorescence staining was performed to validate the transcriptomic results.

RESULTS

We identified three novel subsets of tissue-resident immune cells in the SMGs of patients with IgG4-RD. TOP2A_B cells and TOP2A_T cells had stemness signatures, and trajectory analysis showed that TOP2A_B cells may differentiate into IgG4+plasma cells and that TOP2A_T cells may differentiate into T follicular helper (Tfh) cells. ICOS_PD-1_B cells with Tfh-like characteristics appeared to be an intermediate state in the differentiation from B cells to IgG4+plasma cells. The cellular communication patterns within immune cells and between immune cells and non-immune cells were altered in IgG4-RD compared with controls. Consistently, infection-related pathways were shared in B cells and T cells from SMGs and PBMCs. Furthermore, immune clonotype analysis of PBMC samples showed the complementary determining region 3 amino acid CQQSYSTPYTF was expanded in patients with IgG4-RD.

CONCLUSION

Our data revealed the cellular and molecular changes at the single-cell resolution of IgG4-RD and provide valuable insights into the aetiology and novel therapeutic targets of the autoimmune disease.

Autoimmune Pancreatitis and Immunoglobulin G4-related Sclerosing Cholangitis: Past, Present, and Future

The emergence of glucocorticoid-responsive autoimmune pancreatitis (AIP) and IgG4-related sclerosing cholangitis (IgG4-SC), a new disease entity, has attracted considerable interest within the international gastroenterology community. The typical manifestations of AIP/IgG4-SC are obstructive jaundice and pancreatic enlargement in the elderly, which may mimic the presentations of pancreatobiliary malignancies. The timely diagnosis of AIP/IgG4-SC can lead to adequate glucocorticoid treatment, whereas a misdiagnosis can result in unnecessary major surgery. The diagnostic criteria used to diagnose AIP include several cardinal features of AIP that can be detected via pancreatic parenchymal imaging, ductal imaging, serum IgG4 levels, histopathology, other organ involvement, and response to glucocorticoid therapy. The differential diagnosis of AIP/IgG4-SC may include pancreatobiliary malignancies and primary sclerosing cholangitis. Although most patients with AIP/IgG4-SC respond well to glucocorticoid therapy, there is a frequent relapse of the disease in the long term. This review describes the evolution of the concept of AIP and IgG4-related disease, including the development of diagnostic criteria, discusses the current practice for diagnosis and treatment, and suggests prospects for research.

Interleukin-35 Promotes Th9 Cell Differentiation in IgG4-Related Disorders: Experimental Data and Review of the Literature

IgG4-related disease (IgG4-RD) is characterized by intense infiltration of IgG4-positive plasma cells in affected organs. However, the mechanisms acting in the immune responses in IgG4-RD are not fully understood. The aim of this study was to dissect the mechanism underlying the immunoglobulin class switch in IgG4-RD by addressing the crosstalk between IL-35-producing and Th9 cells. The expression level of IL-35 was examined in plasma samples from patients with hepatobiliary and/or pancreatic manifestations of IgG4-RD. Our data demonstrate that IgG4-RD patients exhibit significantly high-level productions of IL-35 as compared to disease and healthy controls. We detected the two subunits of IL-35, EBI3 and IL-12p35, in the two major affected organs, liver and pancreatic tissue, from IgG4-RD. The EBI3- and IL-12p35-positive cells were significantly higher in affected organs in IgG4-RD as compared to disease controls. The colocalization of EBI3 with CD19 and CD38, markers for B cells, suggest the presence of IL-35-producing B cells in affected organs in IgG4-RD. The effects of IL-35 in Th9 differentiation and IL-9 in production of immunoglobulin were then assessed. Surprisingly, IL-35 treatment promoted naïve CD4 T cell differentiating towards Th9 cells through IRF4 signaling. As a consequence, IL-9 secreted by Th9 cells promoted the differentiation of plasma cells and production of IgG1 and IgG4, predominantly IgG4. In conclusion, our data demonstrate that IL-35 actively participates in the process of inflammation and plays an important role in Th9 differentiation resulting in an immunoglobulin class switch towards IgG4.

The neurology of IGG4-related disease

PURPOSE OF REVIEW

IgG4-related disease (IgG4-RD) is emerging as a fibro-inflammatory entity affecting multiple organs, including manifold neurologic manifestations. This review discusses general characteristics of IgG4-RD neurologic disease including epidemiology, histology, clinical picture and treatment approaches.

RECENT FINDINGS

IgG4-RD is increasingly recognized as an important underlying pathophysiology in multiple disorders of neurologic interest, including orbital inflammation, infundibulo-hypophysitis, hypertrophic pachymeningitis, and even in rare cases CNS parenchymal disease and cranial vascular involvement. These were previously considered idiopathic and unrelated to any systemic disease but now known to share a common histopathology. New knowledge regarding the pathogenesis, clinical features and epidemiology of IgG4 is emerging, and new neurological manifestations continue to be described. Diagnostic progress includes CT-PET imaging, the use of flow cytometry for plasmablast quantification, and the use of reverse passive latex agglutination aiming to overcome the prozone phenomenon. Histopathologic confirmation of IgG4-RD remains the gold standard method of diagnosis but new diagnostic criteria for systemic and organ-specific disease are being proposed. Though glucorticoids remain the mainstay of therapy, relapses and incomplete recovery are frequent. Rituximab is a promising treatment in IgG4-RD that is severe, refractory or glucocorticoid dependent. Initiation of immunosuppression at an early stage of disease should be considered in order to avoid development of refractory fibrosis.

SUMMARY

The current review emphasizes the neurologic manifestations of IgG4-RD.

Combination of autoimmune pancreatitis and peripheral neuropathy on an IgG4-related disease patient with 4 years following-up

Type1 autoimmune pancreatitis (AIP) is the first recognized and the most common manifestation of IgG4-related disease. However, AIP patient presented with neuropathy in the extremities have not been reported previously. We reported a rare combination of autoimmune pancreatitis and peripheral neuropathy on an IgG4-related disease patient based on histological features to expand the clinical spectrum of IgG4-related disease.

The Cellular and Molecular Bases of Allergy, Inflammation and Tissue Fibrosis in Patients with IgG4-related Disease

IgG4-related disease (IgG4-RD) is a spectrum of complex fibroinflammatory disorder with protean manifestations mimicking malignant neoplasms, infectious or non-infectious inflammatory process. The histopathologic features of IgG4-RD include lymphoplasmacytic infiltration, storiform fibrosis and obliterative phlebitis together with increased in situ infiltration of IgG4 bearing-plasma cells which account for more than 40% of all IgG-producing B cells. IgG4-RD can also be diagnosed based on an elevated serum IgG4 level of more than 110 mg/dL (normal < 86.5 mg/mL in adult) in conjunction with protean clinical manifestations in various organs such as pancreato–hepatobiliary inflammation with/without salivary/lacrimal gland enlargement. In the present review, we briefly discuss the role of genetic predisposition, environmental factors and candidate autoantibodies in the pathogenesis of IgG4-RD. Then, we discuss in detail the immunological paradox of IgG4 antibody, the mechanism of modified Th2 response for IgG4 rather than IgE antibody production and the controversial issues in the allergic reactions of IgG4-RD. Finally, we extensively review the implications of different immune-related cells, cytokines/chemokines/growth factors and Toll-like as well as NOD-like receptors in the pathogenesis of tissue fibro-inflammatory reactions. Our proposals for the future investigations and prospective therapeutic strategies for IgG4-RD are shown in the last part.

[Morphological features of IgG4-related lesions at various sites]

OBJECTIVE

To determine the morphological features of IgG4-related lesions and to improve pathomorphological criteria for diagnosing various clinical variants of IgG4-related disease.

MATERIAL AND METHODS

Biopsy and surgical materials from 100 patients with tumor-like lesions at various sites (63 cases of IgG4-related lesion and 37 cases of non-IgG4-related inflammatory processes) were studied. Histological and immunohistochemical studies were conducted to determine the absolute counts of CD138+ cells, IgG+ and IgG4+ in the inflammatory infiltrates, as well as IgG4/IgG and IgG4/CD138 cell ratios.

RESULTS

When IgG4-related disease manifested, pancreatic, lacrimal, and salivary gland lesions prevailed. Brisk lymphoplasmacytic infiltration is characteristic for tissue damage in the eye, salivary glands, thyroid, pancreas, and skin. The formation of moiré fibrosis was specific to damages to the pancreas, liver and bile ducts, and eye tissues. Obliterative phlebitis is most often observed in pancreatic and salivary gland lesions. According to international criteria, the frequency of achieving the required level of IgG4+ plasma cells in each organ was high in lesions of the pancreas, bile ducts, and lymph nodes and that was low in lesions of the salivary and lacrimal glands and skin. The IgG4+/CD138+ and IgG4+/IgG+ cell ratios exceeded 40% in all cases.

CONCLUSION

The morphologic diagnosis of IgG4-related disease is based on the detection of lymphoplasmacytic infiltration, moiré fibrosis, and obliterative phlebitis, as well as on the calculation of the absolute number of IgG4+ plasma cells in the inflammatory infiltrate and on the determination of IgG4+/IgG+ and IgG4+/CD138+ cell ratios. The number of IgG4+ plasma cells depends on the location of the lesion and on the phase of the process.

Highlighting the importance of early diagnosis in progressive multi-organ involvement of IgG4-related disease: A case report and review of literature

IgG4-related disease (IgG4-RD) is an increasingly recognized pathological entity that tends to involve multiple organs with an elevated level of serum IgG4, which is easily misdiagnosed owing to sharing common clinical features with a variety of other diseases. Here, we report an interesting IgG4-RD case of a woman with progressive multi-organ involvement for over 19 years, started with swollen eyelids, dry eye and mouth, and polydipsia and hydruria. Imaging diagnosis revealed diffuse enlargement of the parotid glands, enlargement of the head of the pancreas, pulmonary infection and interstitial lung. Serological tests showed a remarkable elevation of the serum IgG4, and cytological analysis further revealed a large amount of lymphoplasmacytic infiltration into the focal lobule, and IgG4-positive cell infiltration in bladder mucosa. Therapeutically, the patient responded well to steroid therapy, and thus, she was diagnosed as IgG4-RD suspicious. This report highlights the importance of an early diagnosis in this autoimmune disease and suggests that patients with a clinically unclear cause of inflammation, swelling and refractory glands, rhinitis, pancreatitis, hypophysitis, and/or interstitial pneumonia should be considered for IgG4-RD. The plasma IgG4 level and lymphoplasmacytic infiltration may be useful indexes for screening, and a low dose of steroid maintaining therapy may offer benefits for patients with IgG4-RD.

Neuro-ophthalmic complications of IgG4-related disease

PURPOSE OF REVIEW

IgG4-related disease (IgG4-RD) is increasingly recognized as a fibroinflammatory disease with a plethora of organ-specific manifestations but a particular predilection for head and neck tissues, including the nervous system. This review discusses general features and organ-specific presentations of IgG4-RD as well as treatment considerations, particularly emphasizing features of neuro-ophthalmic interest.

RECENT FINDINGS

IgG4-RD is emerging as a common cause of several fibroinflammatory disorders in the head and neck that were previously considered idiopathic, such as sclerosing orbital pseudotumor, orbital myositis, hypophysitis, and hypertrophic pachymeningitis. New and unusual presentations continue to be described, including a number of vascular manifestations. Substantial progress has been made in elucidating the cell types involved in IgG4-RD, and new pathogenic models are being proposed. Although clinicopathologic correlation remains the cornerstone of diagnosis, ancillary tests such as flow cytometry for circulating plasmablasts and PET-computed tomography have high sensitivity, and certain radiologic features are recognized to be particularly suggestive, such as infraorbital nerve enlargement in IgG4-RD orbitopathy. IgG4-RD often responds to steroids but incomplete responses and relapses are common. Rituximab is emerging as a promising new therapy.

SUMMARY

The current review summarizes manifestations of IgG4RD that are of particular relevance to neuro-ophthalmic practice.