Soluble IL-2 receptor, a new marker for autoimmune pancreatitis

Unmet needs in biomarkers for autoimmune pancreatitis diagnosis

Autoimmune pancreatitis (AIP) is a rare chronic autoimmune disorder. The diagnosis of AIP mainly depends on histopathology, imaging and response to treatment. Serum immunoglobulin 4 (IgG4) is used only as collateral evidence in diagnostic criteria for AIP because of its moderate sensitivity. Serum IgG4 levels are normal in 15%-37% of type 1 AIP and most of type 2 AIP patients. In these patients, the indeterminate imaging and histopathology may lead to the difficulty in definitive diagnosis of AIP. Therefore, discovery of new biomarkers is important for AIP diagnosis. Here, we provide some views on the progression and challenges in identifying novel serological biomarkers in AIP diagnosis.

The Clinical Utility of Soluble Serum Biomarkers in Autoimmune Pancreatitis: A Systematic Review

Autoimmune pancreatitis (AIP) is a rare etiological type of chronic pancreatitis. The clinical and radiological presentation of AIP often resembles that of pancreatic cancer. Identifying non-invasive markers for their early distinction is of utmost importance to avoid unnecessary surgery or a delay in steroid therapy. Thus, this systematic review was conducted to revisit all current evidence on the clinical utility of different serum biomarkers in diagnosing AIP, distinguishing AIP from pancreatic cancer, and predicting disease course, steroid therapy response, and relapse. A systematic review was performed for articles published up to August 2021 by searching electronic databases such as MEDLINE, Web of Science, and EMBASE. Among 5123 identified records, 92 studies were included in the qualitative synthesis. Apart from immunoglobulin (Ig) G4, which was by far the most studied biomarker, we identified autoantibodies against the following: lactoferrin, carboanhydrase II, plasminogen-binding protein, amylase-α2A, cationic (PRSS1) and anionic (PRSS2) trypsinogens, pancreatic secretory trypsin inhibitor (PSTI/SPINK1), and type IV collagen. The identified novel autoantigens were laminin 511, annexin A11, HSP-10, and prohibitin. Other biomarkers included cytokines, decreased complement levels, circulating immune complexes, N-glycan profile changes, aberrant miRNAs expression, decreased IgA and IgM levels, increased IgE levels and/or peripheral eosinophil count, and changes in apolipoprotein isoforms levels. To our knowledge, this is the first systematic review that addresses biomarkers in AIP. Evolving research has recognized numerous biomarkers that could help elucidate the pathophysiological mechanisms of AIP, bringing us closer to AIP diagnosis and its preoperative distinction from pancreatic cancer.

Steroid Therapy and Steroid Response in Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP), a unique subtype of pancreatitis, is often accompanied by systemic inflammatory disorders. AIP is classified into two distinct subtypes on the basis of the histological subtype: immunoglobulin G4 (IgG4)-related lymphoplasmacytic sclerosing pancreatitis (type 1) and idiopathic duct-centric pancreatitis (type 2). Type 1 AIP is often accompanied by systemic lesions, biliary strictures, hepatic inflammatory pseudotumors, interstitial pneumonia and nephritis, dacryoadenitis, and sialadenitis. Type 2 AIP is associated with inflammatory bowel diseases in approximately 30% of cases. Standard therapy for AIP is oral corticosteroid administration. Steroid treatment is generally indicated for symptomatic cases and is exceptionally applied for cases with diagnostic difficulty (diagnostic steroid trial) after a negative workup for malignancy. More than 90% of patients respond to steroid treatment within 1 month, and most within 2 weeks. The steroid response can be confirmed on clinical images (computed tomography, ultrasonography, endoscopic ultrasonography, magnetic resonance imaging, and 18F-fluorodeoxyglucose-positron emission tomography). Hence, the steroid response is included as an optional diagnostic item of AIP. Steroid treatment results in normalization of serological markers, including IgG4. Short- and long-term corticosteroid treatment may induce adverse events, including chronic glycometabolism, obesity, an immunocompromised status against infection, cataracts, glaucoma, osteoporosis, and myopathy. AIP is common in old age and is often associated with diabetes mellitus (33-78%). Thus, there is an argument for corticosteroid therapy in diabetes patients with no symptoms. With low-dose steroid treatment or treatment withdrawal, there is a high incidence of AIP recurrence (24-52%). Therefore, there is a need for long-term steroid maintenance therapy and/or steroid-sparing agents (immunomodulators and rituximab). Corticosteroids play a critical role in the diagnosis and treatment of AIP.

Autoimmune pancreatitis: Imaging features

Background and Objectives

Autoimmune pancreatitis (AIP) remains a difficult disease to diagnose before treatment, particularly if presenting as a focal mass lesion. The purpose of this multicenter retrospective study is to analyze imaging features of histologically confirmed AIP to determine the additional diagnostic value of contrast-enhanced ultrasound (CEUS), contrast-enhanced endoscopic ultrasound (CE-EUS), and elastography to B-mode features.

Patients and Methods

We report on a retrospective data collection of 60 histologically confirmed cases of AIP in comparison to 16 patients with pancreatic adenocarcinomas (PDAC). All CE (-E) US examinations were assessed by two independent readers in consensus. The role of CEUS and CE-EUS for pancreatic evaluation was defined according to the 2011 European Federation of Societies for Ultrasound in Medicine and Biology guidelines.

Results

After injection of ultrasound (US) contrast agents, most AIP lesions displayed focal or diffuse isoenhancement (86.6%) in the arterial phase, while most of the PDAC lesions (93.7%) were hypoenhancing (P < 0.01). During the late phase, most AIP lesions were hyper-(65%) or iso-enhancing (35%), while most PDAC lesions were hypoenhancing (93.7%). CE-EUS was performed in a subset of ten patients and showed hyperenhancement in all AIP cases. Most focal AIP lesions (n = 27, 79.4%) were stiffer than the surrounding pancreatic parenchyma.

Conclusions

In this study, percutaneous and endoscopic contrast enhanced harmonic US techniques consistently revealed diffuse and focal types of AIP to have features consistent with vascularized lesions. Differentiation from the typically hypovascularized pancreatic adenocarcinoma was possible with CE (-E) US evaluation.

Enhanced IgG4 production by follicular helper 2 T cells and the involvement of follicular helper 1 T cells in the pathogenesis of IgG4-related disease

Background

The aim of this study was to elucidate the function of circulating follicular helper T (Tfh) cell subsets in helping B cells in patients with active, untreated IgG4-related disease (IgG4-RD) and determine their relationship with disease activity.

Methods

Seventeen consecutive patients with active, untreated IgG4-RD, 20 with primary Sjögren syndrome (pSS), 5 with multicentric Castleman’s disease (MCD), and 12 healthy controls (HC) were enrolled. Tfh cell subset function was evaluated by co-culture with naïve B cells in vitro. Activated Tfh cell subsets were defined as a CCR7^lowPD-1^high subset among Tfh cell subsets. Disease activity was evaluated by IgG4-RD responder index (IgG4-RD RI) score.

Results

The number of Tfh2 cells was significantly higher in IgG4-RD compared to pSS, MCD, or HC, and correlated with serum IgG4 level or the number of plasmablasts. In vitro, Tfh2 cells more efficiently induced the differentiation of naïve B cells into plasmablasts compared to Tfh1 or Tfh17 cells. Of note, while IgG production in culture supernatants of Tfh2 cells was comparable between IgG4-RD and HC, IgG4 production was significantly higher with Tfh2 cells from patients with IgG4-RD than in those from HC. Accordingly, the IgG4:IgG ratio in culture supernatants was also significantly higher with Tfh2 cells from IgG4-RD compared to HC. Moreover, the number of activated Tfh2 cells was higher in IgG4-RD compared to pSS, MCD, or HC, and strongly correlated with IgG4-RD RI score in the baseline active phase. Particularly, the number of activated Tfh2 cells was associated with the number of affected organs and serum IgG4 level. Importantly, the number of activated Tfh2 cells was decreased after glucocorticoid treatment and paralleled disease improvement. Moreover, the number of activated Tfh1 cells was also increased in IgG4-RD compared to pSS, MCD, or HC, correlating with IgG4-RD RI score, but not with serum IgG4 level.

Conclusions

Tfh2 cells, but not Tfh1 or Tfh17 cells, induce the differentiation of naïve B cells into plasmablasts and enhanced production of IgG4 in patients with active, untreated IgG4-RD. Furthermore, activated Tfh2 cells reflect disease activity, suggesting the involvement of this T cell subset in the pathogenesis of IgG4-RD. Interestingly, the number of activated Tfh1 cells was also increased in IgG4-RD, correlating with disease activity but not with serum IgG4 level, suggesting the involvement of Tfh1 cells but not in the process of IgG4 production in patients with IgG4-RD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1064-4) contains supplementary material, which is available to authorized users.

Total lesion glycolysis as an IgG4-related disease activity marker

OBJECTIVES

2-[18F]-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) was reported to be useful for monitoring immunoglobulin G4-related disease (IgG4-RD); however, a quantitative FDG-PET/CT analysis such as total lesion glycolysis (TLG) has not yet been conducted. This study aimed to investigate whether TLG would correlate with serum markers in IgG4-RD, and the utility of TLG for disease monitoring.

METHODS

This retrospective study included 17 patients (12 men; median age, 62 years) who were followed up at Kyoto University Hospital and underwent FDG-PET/CT from April 2009 to November 2013. TLG was calculated for the involved lesions. Correlations between serum markers [IgG4, soluble IL-2 receptor (sIL-2R), lactate dehydrogenase (LDH), and C-reactive protein (CRP)] and TLG concomitant with FDG-PET/CT scans were investigated. Serial changes in TLG were assessed in patients who underwent follow-up FDG-PET/CT (n = 6).

RESULTS

The calculated median (IQL) TLG value was 154.8 (63.7-324.4). A significant correlation was found between the sIL-2R level and TLG (P = 0.001, rs = 0.763). In contrast, no correlations were found between the IgG4, LDH, or CRP levels and TLG. Increased or decreased TLG corresponded with clinical disease improvement or worsening.

CONCLUSIONS

TLG correlated significantly with the serum sIL-2R level and may be useful for disease monitoring in IgG4-RD.

Diagnosis of autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a distinct form of chronic pancreatitis that is increasingly being reported. The presentation and clinical image findings of AIP sometimes resemble those of several pancreatic malignancies, but the therapeutic strategy differs appreciably. Therefore, accurate diagnosis is necessary for cases of AIP. To date, AIP is classified into two distinct subtypes from the viewpoints of etiology, serum markers, histology, other organ involvements, and frequency of relapse: type 1 is related to IgG4 (lymphoplasmacytic sclerosing pancreatitis) and type 2 is related to a granulocytic epithelial lesion (idiopathic duct-centric chronic pancreatitis). Both types of AIP are characterized by focal or diffuse pancreatic enlargement accompanied with a narrowing of the main pancreatic duct, and both show dramatic responses to corticosteroid. Unlike type 2, type 1 is characteristically associated with increasing levels of serum IgG4 and positive serum autoantibodies, abundant infiltration of IgG4-positive plasmacytes, frequent extrapancreatic lesions, and relapse. These findings have led several countries to propose diagnostic criteria for AIP, which consist of essentially similar diagnostic items; however, several differences exist for each country, mainly due to differences in the definition of AIP and the modalities used to diagnose this disease. An attempt to unite the diagnostic criteria worldwide was made with the publication in 2011 of the international consensus diagnostic criteria for AIP, established at the 2010 Congress of the International Association of Pancreatology (IAP).

The clinical characteristics of patients with IgG4-related disease with infiltration of the labial salivary gland by IgG4-positive cells

OBJECTIVES

Mikulicz's disease (MD) is an immunoglobulin (Ig) G4-related disease with systemic symptoms. Submandibular gland (SMG) biopsy is recommended for patients with possible IgG4-related MD for accurate differential diagnosis; however, it is difficult for certain patients to undergo this procedure. In contrast, labial salivary gland (LSG) biopsy is more convenient. Here we present an analysis of patients with IgG4-related MD whose LSG specimens were infiltrated with abundant IgG4-positive plasma cells.

METHODS

Sixteen patients diagnosed with IgG4-related MD underwent simultaneous SMG and LSG biopsies. We evaluated patients' serological and (18)F-fluoro-2-deoxyglucose-positron emission tomography/computed tomography ((18)F-FDG-PET/CT) and grouped them as LSG+ (LSG specimens with > 40% IgG4-positive plasma cells/IgG-positive plasma cells, 11 patients) or LSG- (LSG specimens with < 40% IgG4-positive plasma cells/IgG-positive plasma cells, 6 patients).

RESULTS

There were not significant differences in serum IgG and IgG4 levels between the two groups; however, serum concentrations of soluble interleuikin-2 receptor (sIL-2R) were significantly higher in the LSG+ group. All patients with increased (18)F-FDG uptake in their parotid glands were a part of the LSG+ group.

CONCLUSIONS

When a SMG biopsy is not possible, the serum concentration of sIL-2R and (18)F-FDG-PET/CT findings may predict whether LSG biopsy will facilitate the diagnosis of IgG4-related MD.

Determination of steroid response by abdominal ultrasound in cases with autoimmune pancreatitis

BACKGROUND

Abdominal ultrasound is the most convenient modality for examining the morphology of the pancreas without physical stress. Steroid response is one of the key features of autoimmune pancreatitis; however, visualizing this response has not been evaluated using ultrasonography.

METHODS

Thirty-three consecutive autoimmune pancreatitis cases were retrospectively investigated for pancreatic and extrapancreatic lesions by ultrasonography before steroid therapy (n=33) and at two weeks (n=28) and one month (n=19) after starting oral steroid treatment.

RESULTS

Steroid treatment resulted in obvious shrinkage of the pancreatic lesion in 86% of the cases at two weeks and in 97% until one month. The maximum thickness of the pancreatic lesion was reduced from 28 to 22 mm in two weeks (P<0.0001), and pancreatic echographic findings improved in one month. Swelling of the peripancreatic lymph node was recognized in 48% and the aortic wall thickness in 12%, mostly reduced in two weeks (P=0.005). One case of definitive autoimmune pancreatitis revealed a steroid response only by following endoscopic retrograde cholangiopancreatography but not by ultrasonography or computed tomography.

CONCLUSIONS

Abdominal ultrasound revealed a steroid response in most cases of autoimmune pancreatitis within two weeks. Ultrasonography is suitable for initial confirmation of a steroid response; however, atypical cases showing insufficient response or not fulfilling criteria should undergo further examination.

Reduction of splenic volume by steroid therapy in cases with autoimmune pancreatitis

OBJECTIVES

Splenomegaly is sometimes recognized in autoimmune diseases and chronic pancreatitis; however, it has not yet been studied in autoimmune pancreatitis (AIP). The current study analyzed splenic volume and its associated factors in cases with AIP.

METHODS

Splenic volume was measured using computed tomography (CT) volumetric analysis in 46 cases with AIP and compared with 92 age- and gender-matched controls, and 46 disease controls (liver cirrhosis). Forty-six cases of chronic pancreatitis were also analyzed. Cases with AIP were investigated for factors associated with splenic volume and splenic volume change in response to steroid therapy.

RESULTS

Splenic volume was significantly larger in AIP (149 ± 86 ml) than in controls (97 ± 38 ml) and in CP (108 ± 79 ml) (P < 0.0001 and 0.0002), and was smaller than in disease controls (222 ± 134 ml) (P = 0.003). In AIP cases, splenic volume was associated with age and gender (P = 0.04 and 0.02), and splenomegaly was recognized in 20 % (9/46) of cases. Abnormal uptake of (18)F-fluorodeoxyglucose was not detected in the spleen by positron emission tomography. Splenic vein (SpV) was frequently involved in AIP (67 %), but was all recanalized after steroid therapy. Splenic volume in cases with AIP was minimized to 77 % of the original (122 ± 40 ml) (P < 0.0001) and this trend was remarkable in cases with splenomegaly (66 %). In AIP, high serum IL-2 receptor level, diffuse pancreatic enlargement, and SpV stenosis were significantly associated with splenic shrinkage due to steroid treatment (P = 0.002, 0.02, and 0.03).

CONCLUSIONS

Splenomegaly was sometimes recognized in cases with AIP; however, these cases can be treated with steroids, especially in cases with diffuse pancreatic swelling and SpV stenosis.