Serum BAFF and APRIL levels in patients with IgG4-related disease and their clinical significance. Arthritis Res Ther. 2012;14:R86. [PMID: 22531553 PMCID: PMC3446460 DOI: 10.1186/ar3810]

Mechanisms and assessment of IgG4-related disease: lessons for the rheumatologist

Recognition of IgG4-related disease as an independent chronic inflammatory disorder is a relatively new concept; previously, the condition was thought to represent a subtype of Sjögren's syndrome. IgG4-related disease is characterized by elevated serum levels of IgG4 and inflammation of various organs, with abundant infiltration of IgG4-bearing plasma cells, storiform fibrosis and obliterative phlebitis representing the major histopathological features of the swollen organs. The aetiology and pathogenesis of this disorder remain unclear, but inflammation and subsequent fibrosis occur due to excess production of type 2 T-helper-cell and regulatory T-cell cytokines. The disease can comprise various organ manifestations, such as dacryoadenitis and sialadenitis (also called Mikulicz disease), type 1 autoimmune pancreatitis, kidney dysfunction and lung disease. Early intervention using glucocorticoids can improve IgG4-related organ dysfunction; however, patients often relapse when doses of these agents are tapered. The disease has also been associated with an increased incidence of certain malignancies. Increased awareness of IgG4-related disease might lead to consultation with rheumatologists owing to its clinical, and potentially pathogenetic, similarities with certain rheumatic disorders. With this in mind, we describe the pathogenic mechanisms of IgG4-related disease, and outline considerations for diagnosis and treatment of the condition.

[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.

T helper subsets in Sjögren's syndrome and IgG4-related dacryoadenitis and sialoadenitis: a critical review

IgG4-related disease (IgG4-RD) is a systemic disease characterized by the elevation of serum IgG4 and infiltration of IgG4-positive plasma cells in multiple target organs, including the pancreas, kidney, biliary tract and salivary glands. In contrast, Mikulicz's disease (MD) has been considered a subtype of Sjögren's syndrome (SS) based on histopathological similarities. However, it is now recognized that MD is an IgG4-RD distinguishable from SS and called as IgG4-related dacryoadenitis and sialoadenitis (IgG4-DS). Regarding immunological aspects, it is generally accepted that CD4+ T helper (Th) cells play a crucial role in the pathogenesis of SS. Since it is well known that IgG4 is induced by Th2 cytokines such as interleukin (IL)-4 and IL-13, IgG4-DS is speculated to be a unique inflammatory disorder characterized by Th2 immune reactions. However, the involvement of Th cells in the pathogenesis of IgG4-DS remains to be clarified. Exploring the role of Th cell subsets in IgG4-DS is a highly promising field of investigation. In this review, we focus on the selective localization and respective functions of Th cell subsets and discuss the differences between SS and IgG4-DS to clarify the pathogenic mechanisms of these diseases.

Serum level of APRIL/BLyS in Behçet's disease patients: clinical significance in uveitis and disease activity

OBJECTIVE

The aim of the study reported here was to assess the serum concentration of B-cell activating factors, B lymphocyte stimulators (BLyS), and a proliferation-inducing ligand (APRIL) in Behçet disease (BD) patients in order to evaluate their role and study their relation to uveitis subtype and disease activity.

METHODS

The study included 58 consecutively recruited BD patients with a mean age of 35.54 ± 8.85 years and disease duration of 8.33 ± 5.84 years and 30 age- and sex-matched controls. Disease activity was assessed using the BD current activity form score. Patients were subclassified according to the presence and type of uveitis. Serum BLyS and APRIL were measured by enzyme-linked immunosorbent assay.

RESULTS

Recurrent uveitis was present in 42 (72.41 %) patients, of whom 19 had the anterior form, 13 had the posterior form, and ten had a combined anterior with posterior form; 16 had no eye involvement. Serum APRIL (60.29 ± 57.99 ng/ml) and BLyS (2.31 ± 1.97 ng/ml) levels were significantly higher in the BD patients than in the controls (4.14 ± 4.31 and 0.49 ± 0.39 ng/ml, respectively; P < 0.0001). The levels were clearly higher in those with combined uveitis. The BLyS level significantly correlated with disease activity.

CONCLUSIONS

The overexpression of BLyS and APRIL in BD patients supports the notion of a critical role for B cell activation factors in BD, particularly in terms of uveitis and disease activity. This provides an interesting prospect for the use of anti-BLyS/APRIL antibodies against future therapeutic targets.