Role Of Immunoglobulin G4 Research Articles

The Role of Immunoglobulin G4 in Outcomes of Primary Sclerosing Cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic, cholestatic liver disease that is characterized by an inflammatory and fibrotic process affecting bile ducts which eventually develops into liver cirrhosis and liver failure. The aim of this study was to investigate serum IgG subclass distribution in patients with PSC and its possible association with PSC outcomes. We performed a retrospective analysis of 181 patients who had been diagnosed with PSC between January 1970 and December 2015 and followed at our outpatient clinic. Their demographic, immunological, and clinical characteristics were recorded and analyzed. This study included 181 patients with PSC (120 males, 61 females). There was no association between IgGs and the development of autoimmune hepatitis, cirrhosis, cholangiocarcinoma, liver transplantation, inflammatory bowel disease, and colectomy. Patients with elevated IgG4 had statistically significant higher rates of cholangitis (p = 0.02) and endoscopic retrograde cholangiopancreatography (ERCP) (p = 0.009). High IgG4 values were observed in nine patients who underwent ERCP. In these nine patients, on average, IgG4 was evaluated 5 years after ERCP (min 3 days, max 11 years). Subanalysis considering only IgG4 values evaluated before ERCP showed no significant difference but remains significant if we consider IgG4 values after ERCP. Elevated IgG4 in our study showed a possible association with higher rates of cholangitis and ERCP among patients with primary sclerosing cholangitis. It seems that IgGs may be a useful tool for the prediction of outcomes in patients with PSC. A prospective study is necessary, especially to study the trends of IgGs values during disease as well as the role of possible seroconversion.

The Clinicopathologic Spectrum of IgG4-Related Disease

Immunoglobulin G4-related disease is a fibroinflammatory systemic disease that is characterized by focal or diffuse organ infiltration by immunoglobulin G4-bearing plasma cells. Immunoglobulin G4-related disease may affect any organ, and a high index of suspicion is necessary for early detection to avoid irreversible fibrosis, organ dysfunction, and death. Tumor-forming lesions are common radiological features of immunoglobulin G4-related disease that need to be differentiated from malignancies. The diagnostic approach requires the integration of clinical, biochemical, and radiographic manifestations with classic histopathologic features, which remain crucial to diagnosis. The histology of immunoglobulin G4-related disease is determined by a dense lymphoplasmacytic infiltrate, storiform fibrosis, and obliterative phlebitis in the presence of increased immunoglobulin G4-positve plasma cells. Although immunoglobulin G4-related disease forms a distinct, clinically independent disease category, many questions and problems remain unanswered, especially on its pathogenesis and the role of immunoglobulin G4. Advances in the understanding of immunoglobulin G4-related disease are likely to change the diagnostic approach in the future and create potential targets for therapeutic purposes. Here we describe the concept of immunoglobulin G4-related disease and the most recent knowledge in the clinico-pathological characteristics on this emerging disease. This study can guide clinicians in early diagnosis and prevent unnecessary surgical resections.

Increased immunoglobulin G4–positive plasma cells in collagenous sprue

Collagenous sprue is a rare enteropathy whose etiology is unknown, but immune-mediated mechanisms are one of several possibilities. However, the role of immunoglobulin G4 (IgG4)-positive plasma cells has not been studied in collagenous sprue. Endoscopic biopsies from the duodenum with a histologic diagnosis of collagenous sprue (n = 40 from 35 patients), celiac disease (n = 25), peptic duodenitis (n = 15) and normal duodenum (n = 25) were immunohistochemically stained with IgG4 and CD138 antibodies. For each case, the quantities of IgG4- and CD138-positive plasma cells in the lamina propria were estimated by averaging the number in 3 high-power fields (hpf) that showed the highest concentration. Nine of forty collagenous sprue samples showed a mean of 10 or more IgG4 plasma cells per hpf, whereas none of the duodenal control biopsies showed 10 or more IgG4 plasma cells per hpf: celiac disease (P = .01), peptic duodenitis (P = .05), and normal duodenum (P = .01). Our study demonstrates that increased IgG4-positive plasma cells are present in a subset (23%) of collagenous sprue and may play a role in its pathogenesis.

Involvement of Inducible Costimulator- and Interleukin 10-Positive Regulatory T Cells in the Development of IgG4-Related Autoimmune Pancreatitis

Immunoglobulin G4 (IgG4)-related autoimmune pancreatitis (AIP) is a new clinical entity of pancreatic disorder. There are immunologic and histological abnormalities, including increased serum IgG4 levels and the infiltration of IgG4-positive plasmacytes. However, the role of IgG4 is unclear. Recently, regulatory T cells (Tregs) were reported to contribute to the development of various autoimmune diseases as well as in B-cell shifting to IgG4-producing plasmacytes. We studied Tregs in the pancreas and peripheral blood. We recruited 44 patients with IgG4-related AIP. For comparison, we recruited 37 patients with other pancreatic diseases and 27 healthy subjects as controls. We studied infiltrating cells in the pancreas by immunohistochemistry and analyzed inducible costimulator-positive Tregs and interleukin 10-positive Tregs in the peripheral blood by flow cytometry. The ratio of Foxp3-positive cells to infiltrated mononuclear cells (Foxp3/Mono) in AIP patients was significantly higher than in patients with alcoholic chronic pancreatitis. In AIP, Foxp3/Mono and IgG4/Mono were positively correlated. Inducible costimulator-positive Tregs were significantly higher in AIP patients than in the patients with other pancreatic diseases and the healthy control group. Interleukin 10-positive Tregs were significantly higher in AIP patients than in the healthy control group. Increased quantities of inducible costimulator-positive Tregs may influence IgG4 production in IgG4-related AIP.

Pathophysiology of IgG4-Related Disease

It is still a mystery what is the role of immunoglobulin G4 (IgG4) in IgG4-related disease, or which kinds of immune responses are involved in the pathogenesis. Possible involvement of autoimmunity is supported by the fact that the patients commonly have antinuclear antibodies or hyper γ-globulinemia. The expression of human leukocyte DR antigen in epithelia of the affected organs, and possible reactivity of serum IgG4 of the patients with tissue specimens also support an autoimmune etiology. On the other hand, the Th2-dominant cytokine expression profile resembles allergic disorders rather than classical autoimmune diseases. Another unique point is that many regulatory T-cells infiltrate into the inflamed sites, being associated with the active expression of regulatory cytokines. IL-10 and TGF-β might be the key molecules involved in the two major histological findings of IgG4-related disease: IgG4 class switch and diffuse fibrosis, because IL-10 and TGF-β have a potent function in directing B cells to produce IgG4 and a strong fibrogenic function, respectively. The function of IgG4 in this disorder is still unknown. Unique characters of IgG4 might suggest that IgG4 is not a pathogenetic antibody, but acts as an anti-inflammatory factor by binding to other types of IgG. Recent proteomics studies have discovered possible autoantigens and autoantibodies. Several hypotheses have been proposed so far, but the consensus remains to be reached. Immunopathology in IgG4-related disease is not typical for known disease entities. Keywords: IgG4, autoimmune pancreatitis, cytokine, regulatory T cells, pathology, Systemic lupus erythematosus, Hypophysitis, Chronic sclerosing dacryoadenitis, Chronic sclerosing sialadenitis, Inflammatory pseudotumor, Sclerosing cholangitis

Recognizing Immunoglobulin G4-Related Overlap Syndromes in Patients with Pancreatic and Hepatobiliary Diseases

The first description of autoimmune pancreatitis and elevated serum immunoglobulin-G4 (IgG4) in 2001 heralded further reports of several related autoimmune diseases with raised IgG4 levels. It is now recognized that a spectrum of overlap syndromes associated with increased IgG4 and biopsy evidence of IgG4-producing plasma cells, which has now been convincingly linked with cholangitis, autoimmune hepatitis, Sjögren's syndrome, nephritis and retroperitoneal fibrosis. Collectively, this disease cluster is referred to as IgG4-related systemic disease. The importance of making the correct diagnosis is underscored by the management of individuals with IgG4-related systemic disease. In the first instance, patients generally have a dramatic response to immunosuppressive therapy, whereas patients with other forms of cholangitis and pancreatitis do not. Also, surgical management of pancreatic malignancy can be avoided once the correct diagnosis of IgG4-related disease has been made. In the present review, an overview of the current information regarding the role of IgG4 and IgG4-positive cells affecting the biliary system, pancreas and liver is provided.