Pathogenesis of IgG4-related disease. Curr Opin Rheumatol. 2011;23:114-118. [PMID: 21045701 DOI: 10.1097/bor.0b013e3283412f4a]

Plasmablasts as a biomarker for IgG4-related disease, independent of serum IgG4 concentrations

OBJECTIVES

We examined the utility of circulating total and IgG4+ plasmablasts as biomarkers of diagnosis and disease activity in IgG4-related disease (IgG4-RD).

MATERIALS METHODS

We evaluated patients with active, untreated, biopsy-proven IgG4-RD affecting various organs. Flow cytometry was used to measure total plasmablast and IgG4+ plasmablast counts by gating peripheral blood for CD19lowCD38+CD20-CD27+ cells and CD19lowCD38+CD20-CD27+IgG4+ cells. Serum IgG4 concentrations were measured by nephelometry. We compared 37 IgG4-RD patients to 35 controls, including healthy individuals (n=14) and patients with other inflammatory diseases before treatment (n=21).

RESULTS

The IgG4-RD patients' mean age was 59, and 68% were male. Fourteen patients (38%) had three or more organs involved. The IgG4-RD patients had substantially elevated total plasmablast counts (median 4698/mL, range 610-79524/mL) compared to both untreated disease controls (median 592/mL, range 19-4294/mL; p < 0.001) and healthy controls (median 94/mL, range 1-653/mL; p < 0.001). Thirteen IgG4-RD patients (36%) had normal serum IgG4 concentrations (mean 60 mg/dL, range 5-123 mg/dL, normal <135 mg/dL). However, the median plasmablast count was not significantly lower in that subset with normal serum IgG4 concentrations (3784/mL) compared to those with elevated serum IgG4 (5155/mL) (p = 0.242). Among the 12 rituximab (RTX)-treated patients, the median plasmablast level during disease flare was 6356/mL (range 1123-41589/mL), declining to 1419/mL (range 386/mL-4150/mL) during remission (p < 0.01).

CONCLUSIONS

Circulating plasmablasts are elevated in active IgG4-RD, even in patients with normal serum IgG4 concentrations. Plasmablast counts are a potentially useful biomarker for diagnosis, assessing response to treatment, and determining the appropriate time for re-treatment.

IgG4-related cholecystitis presenting as biliary malignancy: report of three cases

An increased awareness of IgG4-related diseases has led to an escalation in the number of sites known to be involved by this fibroinflammatory disease. We report three cases of IgG4-related cholecystitis which were thought to represent biliary malignancies both clinically and radiographically. All three cases underwent surgery tailored towards presumed malignant neoplasms. Only following pathologic examination was the true nature of the disease identified. Recognition of the clinical, radiographic, and pathologic presentation of IgG4-related cholecystitis is essential for the consideration of this disease process prior to surgical management for suspected gallbladder malignancies. However, the pre-operative diagnosis remains challenging and extensive surgical intervention is often necessary given the distressing presentation of IgG4-related cholecystitis.

Manifestations of immunoglobulin G4 related disease in otolaryngology: case reports and review of the literature

Background:

Immunoglobulin G4 related disease is an inflammatory condition characterised by the presence of fibrotic lesions infiltrated by immunoglobulin G4 positive plasma cells. It can arise from almost any region of the body and it is being increasingly recognised in the head and neck. Regardless of the site of involvement, the histopathological resemblance is remarkable. Dense lymphoplasmacytic infiltration, overabundance of immunoglobulin G4 bearing plasma cells and presence of storiform fibrosis are typical findings.

Case reports:

This paper presents two cases of immunoglobulin G4 related disease in which there was involvement of the orbit, the infraorbital nerve and the infratemporal fossa. Diagnosis was established in both cases by biopsying radiologically abnormal tissue in the infratemporal fossa.

Conclusion:

An awareness of this condition is required to establish the diagnosis and initiate appropriate therapy. Glucocorticoids are the mainstay of initial treatment. The effectiveness of B-lymphocyte depletion with rituximab has also been reported. Correct diagnosis may spare patients from unnecessarily radical surgery.

IgG4-related disease

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is an immune-mediated condition that can affect almost any organ and is now being recognized with increasing frequency. IgG4-RD is characterized by a lymphoplasmacytic infiltrate composed of IgG4(+) plasma cells, storiform fibrosis, obliterative phlebitis, and mild to moderate eosinophilia. The diagnosis of IgG4-RD unifies many eponymous fibroinflammatory conditions that had previously been thought to be confined to single organs. IgG4-RD lesions are infiltrated by T helper cells, which likely cause progressive fibrosis and organ damage. IgG4 antibodies are generally regarded as noninflammatory. Although autoreactive IgG4 antibodies are observed in IgG4-RD, there is no evidence that they are directly pathogenic. Rituximab-induced B cell depletion in IgG4-RD leads to rapid clinical and histological improvement accompanied by swift declines in serum IgG4 concentrations. Although IgG autoantibodies against various exocrine gland antigens have been described in IgG4-RD, whether they are members of the IgG4 subclass is unknown. The contribution of autoantibodies to IgG4-RD remains unclear.

A case of obstructive jaundice due to autoimmune pancreatitis and a review of the literature

A 33-year-old man presented with jaundice, mild pancreatitis, and some weight loss. Laboratory tests showed cholestatic icterus. Imaging revealed distal bile duct obstruction and a mass in the head of the pancreas suspicious for cancer. Besides the enlargement of the head, the whole pancreatic parenchyma was altered. Therefore, autoimmune pancreatitis was considered. Endoscopic ultrasound biopsy found pancreatic tissue with lymphoplasmacytic inflammation and fibrosis. IgG4 serum concentration was within normal range. Due to the benign histology, a therapeutic attempt with prednisolone was initiated. The radiologic changes improved within 2 weeks, which supported the diagnosis of autoimmune pancreatitis. Bile duct obstruction and radiologic abnormalities of the pancreas completely resolved after a 4-month course of steroid treatment. Within 10 months, no relapse occurred. In context with this case, the recent literature was reviewed and the international consensus diagnostic criteria for autoimmune pancreatitis are summarized.

Current status of research on autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis characterized clinically by frequent presentation with obstructive jaundice, histologically by lymphoplasmacytic infiltration with fibrosis, and therapeutically by a dramatic response to steroids. AIP have recently been classified into two subtypes, lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct centric pancreatitis (IDCP). The pathogenesis of AIP may involve genetic susceptibility, autoantibodies, molecular mimicry, imbalance of T-cell-mediated immune regulation, and gene mutation. In this article, we will systematically review typical and atypical clinical, imaging and histopathological features of AIP, with an emphasis placed on the advances in the diagnosis and treatment of this disease.

Possible involvement of CCL1-CCR8 interaction in lymphocytic recruitment in IgG4-related sclerosing cholangitis

BACKGROUND & AIMS

IgG4-related sclerosing cholangitis and type 1 autoimmune pancreatitis (IgG4-SC/AIP) are characterized by massive lymphoplasmacytic infiltration including Th2 and regulatory T cells (Tregs). This study was conducted to address which chemotactic factors are involved in this condition.

METHODS

Chemokine expression profiles in tissue were examined in IgG4-SC/AIP (n=17), classical primary sclerosing cholangitis (IgG4(low) PSC, n=17), PSC with elevated serum/tissue IgG4 levels (IgG4(high) PSC, n=5), and primary biliary cirrhosis (n=7). We focused on five chemotactic factors/receptors (CCL1-CCR8, CCL17/CCL22-CCR4), given that CCR4 and CCR8 are predominantly expressed in both Th2 and Tregs.

RESULTS

In conjunction with higher expression levels of IL-4 and IL-10, expression values of CCL1 and CCR8 transcripts were significantly higher in IgG4-SC/AIP than in IgG4(low) PSC (p=0.002) and IgG4(high) PSC (p=0.023). CCL1 and CCR8 were also overexpressed in IgG4(high) PSC than in IgG4(low) PSC (p=0.023). No difference was seen for CCL17, CCL22, and CCR4. In situ hybridization revealed CCL1 to be predominantly expressed in the pancreatic duct epithelium, peribiliary glands, and vascular endothelial cells including the ones involved in obliterative phlebitis in IgG4-SC/AIP, in contrast to IgG4(high) PSC where this chemotactic factor was positive in several infiltrating lymphocytes. These CCL1-expressing sites were infiltrated by CCR8(+) lymphocytes. On immunohistochemistry, GATA3(+) Th2 lymphocytes and FOXP3(+) Tregs were significantly larger in number in IgG4-SC/AIP, with the GATA3(+)/T-bet(+) cell ratio to be shifted in favour of Th2 in periductal and perivascular areas.

CONCLUSIONS

CCL1-CCR8 interaction may play a critical role in lymphocytic recruitment in IgG4-SC/AIP, leading to duct-centred inflammation and obliterative phlebitis.

[IgG4-related disease]

IgG4-related disease is a systemic fibroinflammatory syndrome of unknown etiology characterized by local inflammatory swelling and tumefactive lesions in one or several organs. It unifies several diseases previously thought to be unrelated. Recently, diagnostic criteria for the disease have been formulated and were complemented by an international consensus on histopathological assessment. In general, the disease activity can be rapidly controlled by high doses of prednisolone (0.6 mg/kg body weight); however, relapses, either local or in other regions, are frequent during tapering of the steroid dose. Commonly used steroid-sparing agents are only partially effective. Persistent local inflammatory activity may result in permanent organ damage. In refractory cases rituximab treatment has been used with good success. In the long-term care of affected patients a probable increased risk of malignancies (e.g. solid tumors and lymphoma) requires attention.

Relationship between Rosai-Dorfman disease and IgG4-related disease: study of 32 cases

OBJECTIVES

To assess the association between Rosai-Dorfman disease (RDD) and IgG4-related disease (IgG4-RD).

METHODS

We studied the number of IgG4-positive plasma cells and the IgG4/IgG ratio in 32 biopsy specimens (13 nodal, 19 extranodal) from 29 patients with RDD and compared the findings with those in IgG4-RD of the pancreas and reactive lymph nodes. We also assessed the number of FOXP3-positive regulatory T cells (Tregs) since they were reported to be increased in IgG4-RD.

RESULTS

We found that RDD cases had much lower numbers of IgG4-positive plasma cells and lower IgG4/IgG ratios compared with IgG4-RD but were similar to reactive lymph nodes. Furthermore, RDD had lower numbers of FOXP3-positive Tregs than did IgG4-RD. There were no significant differences in the number of IgG4-positive plasma cells and the IgG4/IgG ratio between the nodal and extranodal RDD cases.

CONCLUSIONS

Our study suggests that RDD does not belong in the spectrum of IgG4-RD.

The great mimicker: IgG4-related disease

IgG4-related disease is defined as a multi-organ systemic disorder with pathological findings affecting a wide range of organ systems. The condition unifies a large number of clinical diagnoses previously considered as being confined to single organ systems. At present, several issues related to its pathophysiology remained controversial, including the natural history of the disease, the pathogenic role of IgG4, and its use as a biomarker. Glucocorticoids are considered the treatment of choice for remission induction of IgG4-related disease manifestations; however, concerns regarding duration of therapy and management of refractory disease remained to be elucidated.

Development of IgG4-related disease 10 years after chemotherapy for diffuse large B cell lymphoma and longstanding bronchial asthma

Reported is a rare case IgG4-related disease that developed 10 years after combination chemotherapy for non-Hodgkin lymphoma. A 59-year-old Japanese man with longstanding bronchial asthma was referred to our hospital for bilateral hilar lymph node enlargement. The initial diagnosis was diffuse large B cell lymphoma (DLBCL) by supraclavicular lymph node biopsy. Serum IgG was high (4550 mg/dL) at diagnosis. The patient achieved complete response following six cycles of combination chemotherapy. Ten years later, bilateral submaxillary gland swelling was observed. Serum IgG and IgG4 were 2909 and 1470 mg/dL, respectively. The patient was diagnosed with IgG4-related disease by submandibular lymph node biopsy. Due to the difficulty in distinguishing IgG4-related disease from DLBCL through imaging findings alone, pathological confirmation of such lesions by biopsy is mandatory before proceeding to treatment.

IgG4 subclass antibodies impair antitumor immunity in melanoma

Host-induced antibodies and their contributions to cancer inflammation are largely unexplored. IgG4 subclass antibodies are present in IL-10-driven Th2 immune responses in some inflammatory conditions. Since Th2-biased inflammation is a hallmark of tumor microenvironments, we investigated the presence and functional implications of IgG4 in malignant melanoma. Consistent with Th2 inflammation, CD22+ B cells and IgG4(+)-infiltrating cells accumulated in tumors, and IL-10, IL-4, and tumor-reactive IgG4 were expressed in situ. When compared with B cells from patient lymph nodes and blood, tumor-associated B cells were polarized to produce IgG4. Secreted B cells increased VEGF and IgG4, and tumor cells enhanced IL-10 secretion in cocultures. Unlike IgG1, an engineered tumor antigen-specific IgG4 was ineffective in triggering effector cell-mediated tumor killing in vitro. Antigen-specific and nonspecific IgG4 inhibited IgG1-mediated tumoricidal functions. IgG4 blockade was mediated through reduction of FcγRI activation. Additionally, IgG4 significantly impaired the potency of tumoricidal IgG1 in a human melanoma xenograft mouse model. Furthermore, serum IgG4 was inversely correlated with patient survival. These findings suggest that IgG4 promoted by tumor-induced Th2-biased inflammation may restrict effector cell functions against tumors, providing a previously unexplored aspect of tumor-induced immune escape and a basis for biomarker development and patient-specific therapeutic approaches.

IgG4-related diseases

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a fascinating condition recognised as a systemic disease in 2003 [1,2]. The first link between autoimmunity affecting the pancreas, elevated serum IgG4 concentrations and large numbers of IgG4-positive plasma cells in pancreatic tissue was described only 2 years earlier [3]. Since then, many diseases that have long been viewed organ-specific are now considered within the spectrum of IgG4-RD. Practically any organ can be affected, having in common a key pathological feature consisting in dense lymphocyte and plasma cell infiltrate rich in IgG4-positive plasma cells, storiform fibrosis and often an elevated serum IgG4 concentration. While good clinical response to steroid therapy is observed, immunosuppressive or B-cell depleting therapy can be required. It is important to distinguish the IgG4-RD from traditional organ-specific autoimmune disease to guide therapy.

Anti-cytokine autoantibodies suggest pathogenetic links with autoimmune regulator deficiency in humans and mice

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) is a recessive disorder resulting from mutations in the autoimmune regulator (AIRE). The patients' autoantibodies recognize not only multiple organ-specific targets, but also many type I interferons (IFNs) and most T helper type 17 (Th17) cell-associated cytokines, whose biological actions they neutralize in vitro. These anti-cytokine autoantibodies are highly disease-specific: otherwise, they have been found only in patients with thymomas, tumours of thymic epithelial cells that fail to express AIRE. Moreover, autoantibodies against Th17 cell-associated cytokines correlate with chronic mucocutaneous candidiasis in both syndromes. Here, we demonstrate that the immunoglobulin (Ig)Gs but not the IgAs in APECED sera are responsible for neutralizing IFN-ω, IFN-α2a, interleukin (IL)-17A and IL-22. Their dominant subclasses proved to be IgG1 and, surprisingly, IgG4 without IgE, possibly implicating regulatory T cell responses and/or epithelia in their initiation in these AIRE-deficiency states. The epitopes on IL-22 and IFN-α2a appeared mainly conformational. We also found mainly IgG1 neutralizing autoantibodies to IL-17A in aged AIRE-deficient BALB/c mice - the first report of any target shared by these human and murine AIRE-deficiency states. We conclude that autoimmunization against cytokines in AIRE deficiency is not simply a mere side effect of chronic mucosal Candida infection, but appears to be related more closely to disease initiation.

IgG4-related tubulointerstitial nephritis with plasma cell-rich renal arteritis

Immunoglobulin G4 (IgG4)-related tubulointerstitial nephritis is a newly recognized clinicopathologic entity that may occur as an isolated renal lesion or as part of a multisystem disorder. It is characterized by plasma cell-rich interstitial nephritis with abundant IgG4-positive plasma cells and IgG-dominant tubulointerstitial immune deposits. We report the first case of IgG4-related tubulointerstitial nephritis with multifocal plasma cell-rich renal arteritis presenting as acute kidney injury in a 72-year-old man. Seven weeks of prednisone therapy led to nearly complete recovery of kidney function. This case enlarges the morphologic spectrum of this disorder and emphasizes the need to distinguish it from other causes of renal vasculitis.

Extragastric manifestations of Helicobacter pylori infection

In the last year, different diseases possibly linked to Helicobacter pylori infection but localized outside of the stomach have been investigated. There are, in fact, several studies concerning cardiovascular diseases, hematologic disorders, neurologic diseases, metabolic, hepatobiliary diseases, and other conditions. Some of those studies, such as those on sideropenic anemia and idiopathic thrombocytopenic purpura, are quite large and well conducted, while in other cases there are just small or isolated studies or even case reports. Nonetheless, there is much interest among researchers all over the world for such a topic as demonstrated by the large number of studies published in the last year.

Serum BAFF and APRIL levels in patients with IgG4-related disease and their clinical significance

INTRODUCTION

B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) play a crucial role in B cell development, survival, and antibody production. Here we analyzed the serum levels of BAFF and APRIL and their respective clinical associations in patients with an immunoglobulin (Ig) G4-related disease (IgG4-RD).

METHODS

We measured serum levels of BAFF and APRIL in patients with IgG4-RD, primary Sjögren's syndrome (pSS), and healthy individuals. Serum BAFF and APRIL levels in IgG4-RD were assessed for correlations with serological parameters, including Ig, particularly IgG4, and the number of affected organs. Serum BAFF and APRIL levels in IgG4-RD were monitored during glucocorticoid (GC) therapy.

RESULTS

Serum BAFF and APRIL levels in patients with IgG4-RD were significantly higher (P < 0.01) than in healthy individuals. The BAFF levels of patients with IgG4-RD were comparable to those of patients with pSS. Although clinical parameters, such as serum IgG4 and the number of affected organs, were not correlated with the levels of BAFF, serum APRIL levels were inversely correlated with serum IgG4 levels (r = -0.626, P < 0.05). While serum BAFF levels decreased following GC therapy, serum APRIL levels increased during follow-up.

CONCLUSION

These results indicate that BAFF and APRIL might be useful markers for predicting disease activity in IgG4-RD. Further studies are needed to elucidate the role of BAFF and APRIL in the pathogenesis of IgG4-RD.

High serum immunoglobulin G4-related retrosternal fibrosclerosis

A 65-year-old man with a history of exposure to asbestos complained of left leg edema. Computed tomography showed a flat, symmetrical, and longitudinal retrosternal thickening in addition to a presacral tumor. Retroperitoneal fibrosis was suspected. Serum immunoglobulin G4 (IgG4) levels were elevated (213 mg/dL). Thoracoscopic biopsy was performed. Histopathologic findings showed fibrotic tissue accompanied by proliferation of IgG4-positive plasma cells (proportion of IgG4/IgG-positive plasma cells ≥70%) indicative of multifocal fibrosclerosis.

IgG4-related systemic disease: features and treatment response in a French cohort: results of a multicenter registry

IgG4-related systemic disease is now recognized as a systemic disease that may affect various organs. The diagnosis is usually made in patients who present with elevated IgG4 in serum and tissue infiltration of diseased organs by numerous IgG4+ plasma cells, in the absence of validated diagnosis criteria. We report the clinical, laboratory, and histologic characteristics of 25 patients from a French nationwide cohort. We also report the treatment outcome and show that despite the efficacy of corticosteroids, a second-line treatment is frequently necessary. The clinical findings in our patients are not different from the results of previous reports from Eastern countries. Our laboratory and histologic findings, however, suggest, at least in some patients, a more broad polyclonal B cell activation than the skewed IgG4 switch previously reported. These observations strongly suggest the implication of a T-cell dependent B-cell polyclonal activation in IgG4-related systemic disease, probably at least in part under the control of T helper follicular cells.

Immunoglobulin G4 immunostaining of gastric, duodenal, or colonic biopsies is not helpful for the diagnosis of autoimmune pancreatitis

BACKGROUND & AIMS

The aim of this study was to evaluate the specificity of the infiltration of digestive tract mucosa by immunoglobulin (Ig) G4-positive plasma cells in patients with autoimmune pancreatitis (AIP), as compared with normal or inflammatory mucosa.

METHODS

Plasma cell infiltration, CD138 and IgG4 immunostaining of digestive biopsies were compared in 4 groups of patients: AIP type 1 (n = 19); AIP type 2 (n = 4) with inflammatory bowel disease (IBD); IBD without pancreatic disorders (n = 20); and controls (n = 26).

RESULTS

With AIP type 1 versus controls, more plasma cells were present in the gastric mucosa of AIP (P = .02) without difference concerning IgG4+ plasma cells at any biopsy site. With AIP type 1 versus IBD, colonic mucosa was more often abnormal (P = .004), and more CD138 (P = .02) and IgG4 plasma cells (P = .0002) were counted in the colon biopsies of IBD. With AIP type 2 versus IBD, no difference for plasma cell and IgG4 infiltration was found.

CONCLUSIONS

IgG4-positive plasma cells are not more numerous in the digestive mucosa of AIP patients than in controls, but they are more abundant in the colon of IBD patients than in AIP patients.

Type 1 autoimmune pancreatitis

Before the concept of autoimmune pancreatitis (AIP) was established, this form of pancreatitis had been recognized as lymphoplasmacytic sclerosing pancreatitis or non-alcoholic duct destructive chronic pancreatitis based on unique histological features. With the discovery in 2001 that serum IgG4 concentrations are specifically elevated in AIP patients, this emerging entity has been more widely accepted. Classical cases of AIP are now called type 1 as another distinct subtype (type 2 AIP) has been identified. Type 1 AIP, which accounts for 2% of chronic pancreatitis cases, predominantly affects adult males. Patients usually present with obstructive jaundice due to enlargement of the pancreatic head or thickening of the lower bile duct wall. Pancreatic cancer is the leading differential diagnosis for which serological, imaging, and histological examinations need to be considered. Serologically, an elevated level of IgG4 is the most sensitive and specific finding. Imaging features include irregular narrowing of the pancreatic duct, diffuse or focal enlargement of the pancreas, a peri-pancreatic capsule-like rim, and enhancement at the late phase of contrast-enhanced images. Biopsy or surgical specimens show diffuse lymphoplasmacytic infiltration containing many IgG4⁺ plasma cells, storiform fibrosis, and obliterative phlebitis. A dramatic response to steroid therapy is another characteristic, and serological or radiological effects are normally identified within the first 2 or 3 weeks. Type 1 AIP is estimated as a pancreatic manifestation of systemic IgG4-related disease based on the fact that synchronous or metachronous lesions can develop in multiple organs (e.g. bile duct, salivary/lacrimal glands, retroperitoneum, artery, lung, and kidney) and those lesions are histologically identical irrespective of the organ of origin. Several potential autoantigens have been identified so far. A Th2-dominant immune reaction and the activation of regulatory T-cells are assumed to be involved in the underlying immune reaction. IgG4 antibodies have two unique biological functions, Fab-arm exchange and a rheumatoid factor-like activity, both of which may play immune-defensive roles. However, the exact role of IgG4 in this disease still remains to be clarified. It seems important to recognize this unique entity given that the disease is treatable with steroids.

Tissue infiltration of IgG4+ plasma cells in symptomatic patients with ileal pouch-anal anastomosis

BACKGROUND

Inflammatory bowel disease (IBD) is reported to be associated with autoimmune pancreatitis. The aim of the study was to investigate serum IgG4 and tissue infiltration of IgG4+ plasma cells in symptomatic patients with ileal pouches.

METHODS

Ninety-seven consecutive persistent symptomatic patients with ileal pouches from our subspecialty Pouchitis Clinic from January to December 2010 were included in the study. Serum IgG4 was measured at the time of presentation. All patients underwent pouchoscopy with pouch biopsies immunostained for IgG4+ plasma cells. Patients with ≥10 per high-power field of IgG4+ plasma cells were considered positive for the stain.

RESULTS

Twenty-eight (28.9%) patients had positive IgG4 immunostaining of pouch and/or afferent limb biopsy, while the remaining 69 patients (71.1%) were IgG4 negative. Demographic and symptoms were similar between the two groups. The median serum IgG4 in the IgG4 positive group was 21.3 (interquartile range 0-41.3) mg/dL vs. 0 (interquartile range 0-18) in the IgG4 negative group. (p=0.04). On multivariate analysis, the Pouchitis Disease Activity Index (PDAI) endoscopy score in the pouch (odds ratio [OR] 1.66, 95% confidence interval [CI]: 1.21-2.29, p=0.002) and number of concomitant autoimmune disorders (OR 3.04, 95% CI: 1.22-7.53, p=0.017) were independent risk factors for the presence of IgG4+ plasma cell infiltration.

CONCLUSIONS

Increased IgG4+ plasma cells were found in 1/4 of IPAA patients with persistent symptoms. The presence of tissue infiltration of IgG4+ plasma cells appeared to be associated with chronic pouch inflammation and concurrent autoimmune disorders.

Autoimmune pancreatitis characterized by predominant CD8+ T lymphocyte infiltration

Autoimmune pancreatitis (AIP) is a rare form of pancreatitis characterized by prominent lymphocyte infiltration and pancreatic fibrosis resulting in organ dysfunction. The pathogenesis and pathology of AIP remain unknown. A 64-year-old Chinese man presented with symptoms and signs of bile duct obstruction diffuse enlargement of the head of pancreas, elevated IgG levels, and negative autoimmune antibody responses. A pylorus-preserving pancreatoduodenectomy was performed and a pancreatic tumor was suspected. However, periductal lymphoplasmacytic infiltration and fibrosis were found in the head of pancreas and nearby organs instead of tumor cells. Four months after surgery, the patient was readmitted because of reoccurrence of severe jaundice and sustained abdominal distension. Prednisone 30 mg/d was administered orally as an AIP was suspected. One and a half months later, the symptoms of the patient disappeared, and globulin, aminotransferase and bilirubin levels decreased significantly. Over a 9-mo follow-up period, the dose of prednisone was gradually decreased to 10 mg/d and the patient remained in good condition. We further demonstrated dominant CD3+/CD8+ populations, CD20+ cells and a few CD4+ cells in the pancreatic parenchyma, duodenum and gallbladder wall by immunohistochemical assay. This AIP case presented with significant CD8+ T lymphocyte infiltration in the pancreas and extra-pancreatic lesions, indicating that this cell population may be more important in mediating AIP pathogenesis than previously known and that AIP might be a poorly defined autoimmune disease with heterogeneous pathogenesis.

Value of serum IgG4 in the diagnosis of IgG4-related disease and in differentiation from rheumatic diseases and other diseases

IgG4-related disease (IgG4-RD) is a novel disease entity that includes Mikulicz's disease, autoimmune pancreatitis (AIP), and many other conditions. It is characterized by elevated serum IgG4 levels and abundant IgG4-bearing plasmacyte infiltration of involved organs. We postulated that high levels of serum IgG4 would comprise a useful diagnostic tool, but little information is available about IgG4 in conditions other than IgG4-RD, including rheumatic diseases. Several reports have described cutoff values for serum IgG4 when diagnosing IgG4-RD, but these studies mostly used 135 mg/dL in AIP to differentiate from pancreatic cancer instead of rheumatic and other common diseases. There is no evidence for a cutoff serum IgG4 level of 135 mg/dL for rheumatic diseases and common diseases that are often complicated with rheumatic diseases. The aim of this work was to re-evaluate the usual cutoff serum IgG4 value in AIP (135 mg/dL) that is used to diagnose whole IgG4-RD in the setting of a rheumatic clinic by measuring serum IgG4 levels in IgG4-RD and various disorders. We therefore constructed ROC curves of serum IgG4 levels in 418 patients who attended Sapporo Medical University Hospital due to IgG4-RD and various rheumatic and common disorders. The optimal cut-off value of serum IgG4 for a diagnosis of IgG4-RD was 144 mg/dL, and the sensitivity and specificity were 95.10 and 90.76%, respectively. Levels of serum IgG4 were elevated in IgG4-RD, Churg-Strauss syndrome, multicentric Castleman's disease, eosinophilic disorders, and in some patients with rheumatoid arthritis, systemic sclerosis, chronic hepatitis, and liver cirrhosis. The usual cut-off value of 135 mg/dL in AIP is useful for diagnosing whole IgG4-RD, but high levels of serum IgG4 are sometimes observed in not only IgG4-RD but also other rheumatic and common diseases.

Value of serum IgG4 in the diagnosis of IgG4-related disease and in differentiation from rheumatic diseases and other diseases

IgG4-related disease (IgG4-RD) is a novel disease entity that includes Mikulicz's disease, autoimmune pancreatitis (AIP), and many other conditions. It is characterized by elevated serum IgG4 levels and abundant IgG4-bearing plasmacyte infiltration of involved organs. We postulated that high levels of serum IgG4 would comprise a useful diagnostic tool, but little information is available about IgG4 in conditions other than IgG4-RD, including rheumatic diseases. Several reports have described cutoff values for serum IgG4 when diagnosing IgG4-RD, but these studies mostly used 135 mg/dL in AIP to differentiate from pancreatic cancer instead of rheumatic and other common diseases. There is no evidence for a cutoff serum IgG4 level of 135 mg/dL for rheumatic diseases and common diseases that are often complicated with rheumatic diseases. The aim of this work was to re-evaluate the usual cutoff serum IgG4 value in AIP (135 mg/dL) that is used to diagnose whole IgG4-RD in the setting of a rheumatic clinic by measuring serum IgG4 levels in IgG4-RD and various disorders. We therefore constructed ROC curves of serum IgG4 levels in 418 patients who attended Sapporo Medical University Hospital due to IgG4-RD and various rheumatic and common disorders. The optimal cut-off value of serum IgG4 for a diagnosis of IgG4-RD was 144 mg/dL, and the sensitivity and specificity were 95.10 and 90.76%, respectively. Levels of serum IgG4 were elevated in IgG4-RD, Churg-Strauss syndrome, multicentric Castleman's disease, eosinophilic disorders, and in some patients with rheumatoid arthritis, systemic sclerosis, chronic hepatitis, and liver cirrhosis. The usual cut-off value of 135 mg/dL in AIP is useful for diagnosing whole IgG4-RD, but high levels of serum IgG4 are sometimes observed in not only IgG4-RD but also other rheumatic and common diseases.

A novel clinical entity, IgG4-related disease (IgG4RD): general concept and details

IgG4-related disease (IgG4RD) is a novel clinical disease entity characterized by elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. IgG4RD may be present in a certain proportion of patients with a wide variety of diseases, including Mikulicz’s disease, autoimmune pancreatitis, hypophysitis, Riedel thyroiditis, interstitial pneumonitis, interstitial nephritis, prostatitis, lymphadenopathy, retroperitoneal fibrosis, inflammatory aortic aneurysm, and inflammatory pseudotumor. Although IgG4RD forms a distinct, clinically independent disease category and is attracting strong attention as a new clinical entity, many questions and problems still remain to be elucidated, including its pathogenesis, the establishment of diagnostic criteria, and the role of IgG4. Here we describe the concept of IgG4RD and up-to-date information on this emerging disease entity.

Respiratory involvement in IgG4-related Mikulicz's disease

'Immunoglobulin G4 (IgG4)-related disease' is a new clinical concept of multi-organ diseases, with Mikulicz's disease (MD) being a clinical phenotype of IgG4-related disease. To clarify the clinical characteristics of respiratory involvement associated with IgG4-related MD, we retrospectively assessed 25 patients with MD, 11 (44%) of whom had allergic symptoms, and 7 (28%) of whom complained of respiratory problems. Thirteen patients (52%) presented with pulmonary and/or mediastinal lesions (P-MD) on chest computed tomography (CT), and 11 (44%) had lesions limited to the lacrimal and/or salivary glands (L-MD). Mean serum total protein, IgG, and IgG4 concentrations were significantly higher and CH50 was significantly lower in the P-MD than in the L-MD group. Immune complex was present only in the P-MD group. Chest CT images showed bronchial wall thickening, consolidation, nodule(s), interlobular thickening, ground glass opacity, pleural thickening/effusion, and mediastinal lymphadenopathy. Five of seven patients who underwent histological examination of the lungs had abundant IgG4-positive plasma cell infiltrates (IgG4/IgG-positive plasma cells >40%), but the other two did not. These findings suggest that respiratory lesions are not rare in patients with IgG4-related MD, and that they present with various manifestations. IgG4-related MD should be differentiated from similar diseases, such as sarcoidosis, bronchial asthma, Sjögren's syndrome, and malignant lymphoma.