Serum immunoglobulin G4 in Sjögren’s syndrome: a pilot study

Abstract

Immunoglobulin IgG4 plays a role in the pathogenesis of the Mikulicz disease previously considered a form of primary Sjögren's syndrome (pSS). We investigated serum levels of IgG4, total IgG, C3, and C4 serum complementary components in patients suspected of Sjögren's syndrome. Basic laboratory and immunological tests, including IgG4 and IgG concentration, were performed on 20 healthy and 68 suspected of pSS individuals. We distinguished: group I: 48 pSS patients; group II (sicca): 20 patients with dryness without pSS. We revealed: statistical differences between groups I and II concerning hypergammaglobulinemia, ESR, RF, ANA, Ro, and La antibodies; lower IgG4 levels and IgG4/IgG ratio in group I compared to healthy individuals (p < 0.0435; 0.0035, respectively); no significant differences in the concentrations of IgG4 and IgG4/IgG ratio between sicca and control groups. significantly lower (p < 0.0002) C4 levels in group I compared to other groups; significant differences in C4 concentration and IgG4/IgG ratio between three groups (p = 0.0002 and p = 0.0090, respectively); a weak negative correlation between C4 and IgG (r =− 0.274) in the whole database; weak positive correlation between C4 and IgG4/IgG ratio (r = 0.237); a negative correlation of IgG4, IgG4/Ig ratio and C4 with focus score (r = − 0.281; r = − 0.327; r = − 0.406, respectively). IgG4 serum levels were significantly decreased compared to healthy subjects. IgG4 and C4 levels correlated with infiltrations in minor salivary glands. Hypergammaglobulinemia and decreased serum C4 component levels are typical for pSS.

The Role of IgG4 in Autoimmunity and Rheumatic Diseases

“…( 68 ) noted that this group had some features of IgG4-dependent disease. Another study shows a decrease in serum IgG4 concentrations in pSS patients, especially in those with high immune activity and C4 hypocomplementemia ( 69 ).…”

“…Maślińska et al. reported ( 69 ) the lowering of serum concentration of IgG4 below the established normal range in patients with pSS and suggested that it may be also a marker of this autoimmune disease. It was pointed out that C4 hypocomplementemia found in a significant number of pSS patients may have an impact on the reduction of IgG4 concentration and is also an indicator of disease activity taken into account in the ESSDAI assessment ( 88 ).…”

The role of IgG4 in systemic lupus erythematosus: Implications for pathogenesis and therapy

“…MuSK-MG First Ig-like domain in MuSK Prevent Lrp4 from binding MuSK and MuSK phosphorylation [22] Goodpasture syndrome Type IV collagen N.A [23] Iglon-5 TTP Spacer domain of ADAMTS13 Association with relapse [24] CIDP CNTN1 Block interaction of neurofascin 155 with CNTN1 [25] Transverse band loss and paranodal loop detachment Primary membranous nephropathy Neutral endopeptidase Renal involvement [26] Variable degrees of fibrosis SS SS-A Correlation with infiltrations in minor salivary glands [27] SS-B Abbreviations: ADAMTS13, disintegrin and metalloproteinase with thrombospondin motifs 13; CIPD, chronic inflammatory demyelinated polyradiculoneuropathy; CNTN1, contactin 1; MuSK-MG, muscle-specific kinase myasthenia gravis; N.A, not-assessed; SS, Sjögren's syndrome; TTP, thrombotic thrombocytopenic purpura.…”

“…A recent investigation has demonstrated a reduction in serum IgG4 levels among individuals with SS, particularly those exhibiting elevated immune activity and C4 hypocomplementemia. [27] 4 (BCR) and toll-like receptors (TLRs). [45] Upon TLR stimulation, BCR identifies distinct antigens that contain RNA and/or DNA, leading to the production of protein polypeptides and subsequent activation of B cells.…”

“…A recent investigation has demonstrated a reduction in serum IgG4 levels among individuals with SS, particularly those exhibiting elevated immune activity and C4 hypocomplementemia. [ 27 ]…”