Analysis of IgG immune complexes in sera from patients with membranous nephropathy: role of IgG4 subclass and low-avidity antibodies

Lung nodules and IgG4 related disease: a single-center based experience

BACKGROUND

This study was undertaken in an attempt to characterize the frequency and clinical features of lung nodules in IgG4 related disease (IgG4-RD) patients as an insight for help with the diagnosis of lung nodules.

METHODS

A retrospective study was carried out in West China Hospital, Sichuan University from January 2012 to December 2018, 89 patients with definite IgG4-RD were enrolled.

RESULTS

Fifty of 89 patients with definite IgG4-RD had radiologically confirmed lung nodules, 6 of whom were diagnosed with definite IgG4 related lung disease. Lung nodules detected in more than 40 patients were small and solid, always with regular margins. Multiple (41/50) and bilateral (34/50) distributions was also a major characteristic of these lung nodules. Lobulation and speculation were simultaneously detected in 3 patients, including 2 patients combined with pleural indentation. Calcification of nodules was detected in only one patient. Thirty-seven patients also had additional radiological abnormalities of lungs, including ground-glass opacity (21/50), thickening of pleura (9/50), thickening of interlobular septa (4/50), thickening of bronchial wall (3/50), pleural effusion (4/50), mass (3/50), interstitial changes (5/50), and mediastinal or hilar lymphadenopathy (32/50). Most patients (44/50) were treated with glucocorticoids alone or combined with immunosuppressive agents. Sixteen patients received a re-examination by chest computed tomography (CT) scan after treatment, 10 of whom showed a decrease in the size and/or the number of nodules.

CONCLUSIONS

The incidence of lung nodules in IgG4-RD patients can be high. For an IgG4-RD patient with lung nodules, the possibility that the lung nodules related to IgG4-RLD is high. It is hard to differentiate IgG4 related lung nodules from other lung diseases, in particular, lung cancer. Radiological characteristics and positive responses to glucocorticoids and immunosuppressive agents can help with the differential diagnosis. For these patients, regular follow-up is also important.

[Diagnostic value of IgG subtypes in membranous nephropathy: A case report]

The study of immunoglobulin G subtypes constituting immune deposits present in membranous nephropathy is useful to guide diagnosis. IgG4 deposits are more often seen in primitive forms of membranous nephropathy due to autoantibody (anti-phospholipase A2 receptor in a majority of cases). These deposits are polytypic. In secondary forms, deposits are constituted of IgG1, IgG2 and IgG3. We report the case of a 52-year-old woman whose renal biopsy, done for glomerular proteinuria, shows membranous nephropathy with monotypic IgG4 deposits with no overt hematologic malignancy and no anti-PLA2R antibodies.

Synovitis in a Patient with IgG4-related Disease

A 71-year-old man was admitted to our department due to arthralgia and renal dysfunction. A physical examination disclosed swelling of the right shoulder and left wrist joints. Laboratory tests showed elevated serum IgG4 and creatinine levels, and magnetic resonance imaging of the wrist revealed bone erosion and synovitis. In addition, fluorodeoxyglucose positron emission tomography showed uptake in the submandibular glands, pancreas, kidneys, and affected joints and a renal biopsy revealed tubulointerstitial nephritis with the infiltration of IgG4+ plasma cells. The patient was subsequently diagnosed with IgG4-related disease (IgG4-RD) and successfully treated with corticosteroid therapy. This case suggests that erosive arthritis may occur in patients with IgG4-RD.

Characteristic tubulointerstitial nephritis in IgG4-related disease

Nephropathy associated with IgG4-related disease is characterized by tubulointerstitial nephritis. To better identify its pathology, the present study analyzed clinicopathologic features of IgG4-related tubulointerstitial nephritis cases from across Japan. Sixteen cases were identified as IgG4-related nephropathy using the criterion of high serum IgG4 levels (>135 mg/dL) with abnormal kidney computed tomography or elevated serum creatinine levels. Male predominance (75%) and advanced age (average, 62.0 years) were noted. Eight cases displayed no autoimmune pancreatitis. Renal computed tomography abnormalities were found in 12 of 13 cases examined. Renal dysfunction was found in 15 of 16 cases at biopsy. Distinctive features of tubulointerstitial lesions included (1) well-demarcated borders between involved and uninvolved areas; (2) involvement of the cortex and medulla, often extending beyond the renal capsule and with occasional extension to retroperitoneal fibrosis; (3) interstitial inflammatory cells comprising predominantly plasma cells and lymphocytes, with a high prevalence of IgG4-positive cells often admixed with fibrosis; (4) peculiar features of interstitial fibrosis resembling a "bird's-eye" pattern comprising fibrosis among inter-plasma cell spaces; and (5) deposits visible by light and immunofluorescent microscopy in the tubular basement membrane, Bowman capsule, and interstitium that are restricted to the involved portion, sparing normal parts. Ultrastructural analysis revealed the presence of myofibroblasts with intracellular/pericellular collagen accompanied by plasma cell accumulation from an early stage. Histology could not discriminate between IgG4-related tubulointerstitial nephritis with and without autoimmune pancreatitis. In conclusion, the distinctive histologic features of IgG4-related tubulointerstitial nephritis can facilitate the differential diagnosis of tubulointerstitial nephritis, even without autoimmune pancreatitis or an abnormal computed tomography suggesting a renal tumor.

Effects of rituximab on morphofunctional abnormalities of membranous glomerulopathy

BACKGROUND AND OBJECTIVES

In idiopathic membranous nephropathy (IMN), CD(20) B-cell depletion by rituximab may induce nephrotic syndrome (NS) remission. Whether this is associated with kidney function restoration and regression of the glomerular pathology was evaluated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Treatment-induced morphofunctional changes were evaluated in 7 IMN patients consenting to repeat functional and morphologic evaluations after stable disease remission achieved by four weekly rituximab (375 mg/m(2)) infusions.

RESULTS

Over a median of 21 mo from rituximab administration, NS remission was associated with 8.5-fold increase versus baseline in sodium fractional clearance from 1.56 to 13.25, decrease in renal plasma flow from 440.8 to 276.6 ml/min per 1.73 m(2), stable glomerular filtration rate, and increased renal vascular resistances. Changes in sodium fractional clearance and hemoglobin concentration were positively correlated (r = 0.82). Biopsy reevaluations showed complete or partial reabsorption of subepithelial deposits. Median (interquartile range) IgG4 staining score decreased from 3 (3-3) to 1 (0-2), whereas total numbers of slit diaphragms (0.27; range, 0.19 to 0.30 versus 0.86; range, 0.53 to 1.16 slits/mum glomerular basement membrane) and percentages of those with electron-dense diaphragm (55.2; range, 42.0 to 62.0 versus 78.5; range, 73.0 to 82.7 of all slits) significantly increased in parallel with amelioration of glomerular ultrastructural changes. Changes in slit frequency and albumin fractional clearance were negatively correlated (r = -0.79).

CONCLUSIONS

In human IMN, treatment-induced NS remission is associated with restoration of sodium homeostasis and kidney hemodynamics, and regression of the glomerular changes underlying proteinuria. These effects are likely to translate into long-term renoprotection.

Th2 cytokines increase and stimulate B cells to produce IgG4 in idiopathic membranous nephropathy

BACKGROUND

The predominant deposition of IgG4 in idiopathic membranous nephropathy indicates that its presence characterizes the systemic immune response of the disease.

METHODS

We analyzed the expressions of CD3, CD19, CD4, and CD8 on peripheral blood mononuclear cells (PBMCs) by flow cytometry, and the levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), interferon (IFN)-gamma, interleukin (IL)-4, IL-10, and IL-13 mRNAs in PBMCs using real-time reverse transcription-polymerase chain reaction (RT-PCR) in 14 patients with idiopathic membranous nephropathy and 14 normal control donors. The levels of IgG subclasses in the B-cell culture supernatant in the presence or absence of cytokines were quantified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Idiopathic membranous nephropathy patients showed an increased CD4(+)/CD8(+) ratio, although the numbers of peripheral T and B cells were comparable to those of the normal control group. IL-10 and IL-13 mRNA expression levels increased in the idiopathic membranous nephropathy group. The levels of spontaneous production of each IgG subclass by B cells were identical in the two groups. In the presence of Th2 cytokines, B cells from several individuals of the idiopathic membranous nephropathy group augmented the production of IgG4. When the individual levels of each IgG subclass in the presence of cytokines were compared with those in the absence of cytokines in each sample, a significant increase in the production of IgG4 in the presence of IL-4 was observed in the idiopathic membranous nephropathy group.

CONCLUSION

These results indicate that the altered functions of T cells to produce Th2 cytokines and the increased production of IgG4 by B cells in response to these cytokines characterize the immune response in idiopathic membranous nephropathy.

Autoimmune pancreatitis is closely associated with gastric ulcer presenting with abundant IgG4-bearing plasma cell infiltration

BACKGROUND

Autoimmune pancreatitis is characterized by high serum IgG4 concentrations and lymphoplasmacytic infiltration. Because of the diversity of extrapancreatic involvement in this disease, the present study sought to identify other associated GI-tract lesions.

METHODS

EGD findings were compared between a group of 23 patients with autoimmune pancreatitis undergoing ERCP for obstructive jaundice and 230 age- and gender-matched control patients. To clarify the histopathologic differences found between these two groups, the histopathologic findings (Updated Sydney System) and the immunohistochemistry of each IgG subclass were compared between 8 patients with autoimmune pancreatitis and gastric ulcer, and 23 control patients with gastric ulcer from which biopsy specimens had been obtained.

RESULTS

Gastric ulcer was found significantly more frequently in patients with autoimmune pancreatitis compared with control patients (34.8% vs. 13.5%; p=0.007). There was no significant difference between the groups with respect to the frequency of other GI lesions. Four of 8 gastric ulcers in patients with autoimmune pancreatitis were linear, with the long axis perpendicular to the incisura on the lesser curvature of the stomach. The activity score for the gastric lesions was significantly lower in patients with autoimmune pancreatitis compared with control patients (mean score 0.38 vs. 1.08; p=0.012). There were no significant differences in histopathologic findings with respect to inflammation, atrophy, metaplasia, or Helicobacter pylori scores between the two groups. IgG4-bearing plasma cells were significantly more abundant in gastric lesions in patients with autoimmune pancreatitis compared with those in control patients (mean score 1.75 vs. 0.39; p=0.0008).

CONCLUSIONS

Autoimmune pancreatitis is closely associated with gastric ulcer with abundant IgG4-bearing plasma cell infiltration.

High serum IgG4 concentrations in patients with sclerosing pancreatitis

BACKGROUND

Sclerosing pancreatitis is a unique form of pancreatitis that is characterized by irregular narrowing of the main pancreatic duct, lymphoplasmacytic inflammation of the pancreas, and hypergammaglobulinemia and that responds to glucocorticoid treatment. Preliminary studies suggested that serum IgG4 concentrations are elevated in this disease but not in other diseases of the pancreas or biliary tract.

METHODS

We measured serum IgG4 concentrations using single radial immunodiffusion and an enzyme-linked immunosorbent assay in 20 patients with sclerosing pancreatitis, 20 age- and sex-matched normal subjects, and 154 patients with pancreatic cancer, ordinary chronic pancreatitis, primary biliary cirrhosis, primary sclerosing cholangitis, or Sjögren's syndrome. Serum concentrations of immune complexes and the IgG4 subclass of immune complexes were determined by means of an enzyme-linked immunosorbent assay with monoclonal rheumatoid factor.

RESULTS

The median serum IgG4 concentration in the patients with sclerosing pancreatitis was 663 mg per deciliter (5th and 95th percentiles, 136 and 1150), as compared with 51 mg per deciliter (5th and 95th percentiles, 15 and 128) in normal subjects (P<0.001). The serum IgG4 concentrations in the other groups of patients were similar to those in the normal subjects. In patients with sclerosing pancreatitis, serum concentrations of immune complexes and the IgG4 subclass of immune complexes were significantly higher before glucocorticoid therapy than after four weeks of such therapy. Glucocorticoid therapy induced clinical remissions and significantly decreased serum concentrations of IgG4, immune complexes, and the IgG4 subclass of immune complexes.

CONCLUSIONS

Patients with sclerosing pancreatitis have high serum IgG4 concentrations, providing a useful means of distinguishing this disorder from other diseases of the pancreas or biliary tract.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.

Membranous nephropathy: an IgG4-mediated disease

Membranous nephropathy is characterised by the deposition of immunoglobulin, predominantly of the IgG4 subclass, along the epithelial surface of the glomerular-basement membrane. Current models of pathogenesis usually assume in-situ immune-complex formation involving an as yet uncharacterised fixed glomerular antigen. I argue that the properties of IgG4 (inability to fix complement and therefore impaired clearance of IgG4-containing complexes; low affinity and therefore ability for IgG4-containing complexes to dissociate and traverse the glomerular-basement membrane) are compatible with a pathogenic mechanism that involves the deposition of circulating IgG4 immune complexes containing diverse antigens.