Role of the IgG4-related cholangitis autoantigen annexin A11 in cholangiocyte protection

BACKGROUND & AIMS

Annexin A11 was identified as autoantigen in IgG4-related cholangitis (IRC), a B-cell driven disease. Annexin A11 modulates calcium-dependent exocytosis, a crucial mechanism for insertion of proteins into their target membranes. Human cholangiocytes form an apical 'biliary bicarbonate umbrella' regarded as defense against harmful hydrophobic bile acid influx. The bicarbonate secretory machinery comprises the chloride/bicarbonate exchanger AE2 and the chloride channel ANO1. We aimed to investigate the expression and function of annexin A11 in human cholangiocytes and a potential role of IgG1/IgG4-mediated autoreactivity against annexin A11 in the pathogenesis of IRC.

METHODS

Expression of annexin A11 in human liver was studied by immunohistochemistry and immunofluorescence. In human control and ANXA11 knockdown H69 cholangiocytes, intracellular pH, AE2 and ANO1 surface expression, and bile acid influx were examined using ratio microspectrofluorometry, cell surface biotinylation, and 22,23-3H-glycochenodeoxycholic acid permeation, respectively. The localization of annexin A11-mEmerald and ANO1-mCherry was investigated by live-cell microscopy in H69 cholangiocytes after incubation with IRC patient serum containing anti-annexin A11 IgG1/IgG4-autoantibodies or disease control serum.

RESULTS

Annexin A11 was strongly expressed in human cholangiocytes, but not hepatocytes. Knockdown of ANXA11 led to reduced plasma membrane expression of ANO1, but not AE2, alkalization of intracellular pH and uncontrolled bile acid influx. High intracellular calcium conditions led to annexin A11 membrane shift and colocalization with ANO1. Incubation with IRC patient serum inhibited annexin A11 membrane shift and reduced ANO1 surface expression.

CONCLUSION

Cholangiocellular annexin A11 mediates apical membrane abundance of the chloride channel ANO1, thereby supporting biliary bicarbonate secretion. Insertion is inhibited by IRC patient serum containing anti-annexin A11 IgG1/IgG4-autoantibodies. Anti-annexin A11 autoantibodies may contribute to the pathogenesis of IRC by weakening the 'biliary bicarbonate umbrella'.

LAY SUMMARY

We previously identified annexin A11 as a specific autoantigen in immunoglobulin G4-related cholangitis (IRC), a B-cell driven disease affecting the bile ducts. Human cholangiocytes are protected against harmful hydrophobic bile acid influx by a defense mechanism referred to as the 'biliary bicarbonate umbrella'. We found that annexin A11 is required for the formation of a robust bicarbonate umbrella. Binding of patient-derived annexin A11 autoantibodies inhibits annexin A11 function, possibly contributing to bile duct damage by weakening the biliary bicarbonate umbrella in patients with IRC.

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.

IgG4-related disease with multiorgan involvement: a case-based review

IgG4-related disease (IgG4-RD) is an immune-mediated multi-organ inflammatory disorder caused by tissue infiltration of lymphocytes with IgG4-secreting plasma cells. Herein, we discuss a case of a patient with IgG4-RD who had involvement of multiple organs: the kidneys, lymph nodes, bone marrow (biopsy performed), lungs, liver, and small intestine (imaging abnormalities). Although several case reports and series of IgG4-RD involving different organ involvement are in the literature, our patient has extensive simultaneous multi-organ involvement. We utilized the four domains (serologic, pathologic, radiologic, and pathologic) as discussed in the new 2019 ACR/EULAR classification criteria to provide a useful framework in considering an alternative tool for IgG4-RD in multi-organ involvement, where biopsy is more invasive and not always accessible. We highlight the findings of each organ involved that increase the likelihood that the patient has IgG4-RD. In our patient, the IgG4-RD classification criteria was fulfilled with total points adding up to 48. Our case meets the classification criteria for IgG4-RD, since at least one organ is involved to meet entry criteria (biopsy proven), no exclusion criteria are present, and the total points are ≥ 20. When such extensive involvement of IgG4-RD occurs, early diagnosis and treatment are recommended to avoid irreversible organ damage and better outcomes.

Advances in the diagnosis and management of IgG4 related disease

IgG4 related disease was recognized as a unified disease entity only 15 years ago. Awareness of IgG4 related disease has increased worldwide since then, and specialists are now familiar with most of its clinical manifestations. Involvement of the pancreato-biliary tract, retroperitoneum/aorta, head and neck, and salivary glands are the most frequently observed disease phenotypes, differing in epidemiological features, serological findings, and prognostic outcomes. In view of this multifaceted presentation, IgG4 related disease represents a great mimicker of many neoplastic, inflammatory, and infectious conditions. Histopathology remains key to diagnosis because reliable biomarkers are lacking. Recently released classification criteria will be invaluable in improving early recognition of the disease. IgG4 related disease is highly treatable and responds promptly to glucocorticoids, but it can lead to end stage organ failure and even death if unrecognized. Prolonged courses of corticosteroids are often needed to maintain remission because the disease relapses in most patients. Rapid advancement in our understanding of the pathophysiology of IgG4 related disease is leading to the identification of novel therapeutic targets and possible personalized approaches to treatment.

Sclerosing Mesenteritis Mimicking IgG4-related Disease

A 72-year-old man was followed as an outpatient at our hospital for 6 years after surgery for small cell carcinoma of left adrenal gland origin. Follow-up abdominal computed tomography showed a 6-cm mass in the left lower mesentery. The patient underwent open laparotomy. The histological diagnosis was sclerosing mesenteritis. The previous specimens of the left adrenal mass were then re-examined with a microscope, and panniculitis was found around the small cell carcinoma. Both lesions were histologically similar to IgG4-related disease (RD), but they did not completely meet the diagnostic criteria of IgG4-RD clinically or histologically.

Recurrent myelitis and asymptomatic hypophysitis in IgG4-related disease: case-based review

IgG4-related disease (IgG4-RD) is a disorder with various clinical manifestations. Central nervous system (CNS) involvement is well recognized, with hypertrophic pachymeningitis and hypophysitis being the most common manifestations. Spinal cord involvement is an extremely rare manifestation. We present the first case of an IgG4-RD patient with spinal cord parenchymal disease and concurrent hypophysitis. We review also the current literature about CNS parenchymal involvement in the context of IgG4-RD. A young female presented with clinical symptoms of myelitis. Cervical spinal cord magnetic resonance imaging (MRI) displayed features of longitudinally extensive transverse myelitis (LETM). Brain MRI showed a small number of high-intensity lesions in the deep white matter and enlargement of hypophysis with homogeneous gadolinium enhancement (asymptomatic hypophysitis). Diagnostic workup revealed elevated IgG4 serum levels (146 mg/dL). Our patient fulfilled the organ-specific diagnostic criteria of IgG4-hypophysitis. Treatment with intravenous glucocorticoids led to rapid clinical response, and to the substantial resolution of imaging findings. Azathioprine was used as a maintenance treatment. One relapse occurred 2 years after the initial diagnosis and patient was re-treated with glucocorticoids. Three years after relapse, patient is in remission with azathioprine. We present the first case of myelitis with radiological features of LETM associated with increased IgG4 serum levels and the simultaneous presence of asymptomatic IgG4-related hypophysitis.

Coexistence of nontuberculous mycobacterium and IgG4-related disease in a solitary pulmonary nodule: A case report

RATIONALE

Immunoglobulin G4-related disease (IgG4-RD) is regarded as an immune-mediated systemic fibroinflammatory disease. Several studies have linked IgG4-RD to infections such as tuberculosis and actinomycosis. However, the coexistence of IgG4-RD and non-tuberculous mycobacterium (NTM) in a single pulmonary nodule has not been reported yet.

PATIENT CONCERNS

A 76-year-old male patient presented with cough and sputum. A solitary pulmonary nodule suspicious of lung cancer was found on chest CT.

DIAGNOSIS

Through video-assisted thoracoscopic biopsy, a diagnosis of co-existing NTM and IgG4-RD in a single nodule was made.

INTERVENTIONS

Antibiotic treatment was applied for pneumonia developed after surgery. The patient was also supported by extracorporeal membrane oxygenation and mechanical ventilation since his pneumonia was refractory to medical treatment.

OUTCOMES

The patient expired on the 60th postoperative day due to multiple organ failure.

LESSONS

IgG4-RD can occur singularly or accompanied by other diseases. We report a solitary pulmonary nodule caused by NTM and concurrent IgG4-RD, suggesting a possible association between these 2 entities. Immunologic relations between IgG4-RD and accompanying infection should be further investigated.

IgG4-related Disease Involving the Cardiovascular System: An Intracardiac Mass and a Mass Lesion Surrounding a Coronary Artery

A 61-year-old Japanese man with IgG4-related autoimmune pancreatitis developed a mass in the right atrium (RA) and a mass lesion surrounding the left anterior descending coronary artery. We performed an intracardiac echo catheter-guided percutaneous biopsy of the RA mass, and histologically diagnosed it as IgG4-related disease. Oral corticosteroid therapy gradually downsized the mass lesions. We encountered a very rare case with mass lesions in the cardiovascular system of the IgG4-related disease that were able to be diagnosed using an intracardiac echo-guided biopsy.

Progression of immunoglobulin G4-related disease to systematic lupus erythematosus after gastric cancer surgery: A case report

RATIONALE

Immunoglobulin G4 related disease (IgG4-RD) rarely coexists with other autoimmune diseases, though we had a patient whose primary clinical problem was shifted from IgG4-RD to systemic lupus erythematosus (SLE) after gastrectomy. The present paper aimed to report pathological findings and clinical course of the patient.

PATIENT CONCERNS

The patient was a male aged 74 years old with gastric cancer characterized by the following symptoms: Raynaud phenomenon, polyarthralgia, and swollen parotid glands on both sides. Before gastrectomy, laboratory examination results showed renal dysfunction, hypocomplementemia, antinuclear antibodies (ANAs) positivity, and elevated serum IgG and IgG4 levels.

DIAGNOSIS

Based on postoperative renal biopsy showing severe plasma cell infiltration with tubulointerstitial fibrosclerosis, the patient was diagnosed with IgG4-RD. Despite significant improvement in renal function and reduction in parotid gland swelling during the postoperative follow-up period, after 7 months of the gastrectomy, anti-DNA antibody levels were increased and serositis was detected, which indicated the onset of SLE. IgG4-type ANA were also detected in the sera of the patient.

INTERVENTIONS

Treatment by oral prednisolone at 30 mg/day was initiated.

OUTCOMES

Pericardial fluid, pleural effusions, and thickening of the gallbladder wall improved after 3 months of treatment according to computed tomography.

LESSONS

This study presented a rare case of comorbidity, wherein the patient's primary problem progressed from IgG4-type ANA-positive IgG4-RD to SLE after excision of gastric cancer.