Expression of the Inherently Autoreactive Idiotope 9G4 on Autoantibodies to Citrullinated Peptides and on Rheumatoid Factors in Patients with Early and Established Rheumatoid Arthritis

Abstract

BackgroundThe pre-symptomatic stage of Rheumatoid arthritis (RA) is associated with pro-inflammatory cytokines and autoantibodies. High levels and epitope spread by Rheumatoid factors (RhF) and autoantibodies to citrullinated proteins signify progression towards disease expression. In established RA, the persistence of high autoantibody levels reflects production by both long-lived plasma cells and short-lived plasmablasts. Neither the relative contributions to pathogenesis by autoantibodies from either source, nor the factors responsible for deciding the fate of autoantigen specific ‘parent’ B-cells, is understood. Phenotypic markers identifying subsets of autoreactive B-cells are therefore of interest in understanding the origin and perpetuation of the autoimmune response in RA. One such phenotypic marker is the rat monoclonal antibody, 9G4, which recognises an idiotope on immunoglobuins derived from the inherently autoreactive VH-gene, VH4-34. We therefore investigated whether the 9G4 idiotope was expressed on autoantibodies in patients with RA.Methodology/Principal FindingsSera from 19 patients with established RA and those with <1year history of untreated polyarthritis either resolving into RA (n = 42) or non-RA diagnosis (n = 31) were included. Autoantibodies to cyclic citrullinated peptides (CCP), RhF and co-expression of the 9G4 idiotope were measured by ELISA. 9G4 recognised a population of anti-CCP antibodies in the majority of sera from patients with established disease and also in samples from patients with early disaese. 9G4+RhF levels were generally lower and not associated with positivity for, or levels of 9G4+CCP.Conclusions/SignificanceThe persistence of 9G4+ immunoglobulins, of any isotype, in serum is rare. We describe here the novel finding of 9G4 expression on anti-CCP antibodies in patients from the earliest symptoms of RA through to established disease. Our results suggest that 9G4 expression on anti-CCP autoantibodies was not due to polyclonal expansion of VH4-34-encoded immunoglobulins. These studies may therefore provide a new focus for investigation into the evolution of the autoimmune response in RA patients.

Activation-induced deaminase is critical for the establishment of DNA methylation patterns prior to the germinal center reaction

“…To assess this hypothesis, we first checked whether there is an expansion of naïve autoreactive B cells in HIGM2 patients with respect to controls. To this end, we used a commercial antibody against 9G4 + IgG used to detect autoreactive clones in autoimmune diseases like systemic lupus erythematosus and rheumatoid arthritis [65][66][67][68] . We observed an expansion the naïve B cell compartment in HIGM2 patients in comparison with healthy controls (Fig.…”

Antibodies to Cyclic Citrullinated Peptides in Patients With Juvenile Idiopathic Arthritis and Patients With Rheumatoid Arthritis: Shared Expression of the Inherently Autoreactive 9G4 Idiotype

“…IgA anti-CCP are rarely observed in healthy control sera (21) and cutoff was therefore based on calculations using the mean 1 3SD of binding by 60 sera from healthy controls across all age groups (giving a value of 11 AU/ml) (21). Results were expressed as a proportion of the positive control following subtraction of background binding of HRP conjugate and normalization between different ELISA plates.…”

“…V H 4–34 usage is, for example, obligatory for most cold agglutinins , utilized by some IgG anti–double‐stranded DNA antibodies in serum, and also found deposited in renal biopsy specimens from patients with systemic lupus erythematosus (SLE) and used by antimyeloperoxidase antibodies in systemic vasculitis . More recently, we have described 9G4‐positive autoantibodies specific for CCP in patients with early RA (<6 weeks of joint symptoms) and those with established RA . Investigating the isotype distribution and presence of the 9G4 idiotope on anti‐CCP antibodies in RF‐positive polyarticular JIA and comparing this to a local seropositive adult RA population may therefore further our understanding of potential common pathways for autoreactive B cell selection in RF‐positive polyarticular JIA.…”

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

“…A number of the results demonstrate that the situation with the polyclonal lymphocyte activation in RA is complicated. The data of recent studies, which tested the isotype distribution, antigen specifity and affinity of the serum and synovial fluid RFs and anti-CCP Abs as well as the expression of the inherently autoreactive idiotope 9G4 in preclinical, early and advanced stages of RA, failed to clarify whether such a process is crucial in RA development ( Moyes et al, 1996 ; Verpoort et al, 2006 , Ioan-Facsinay et al, 2008 ; Cambridge et al, 2014 , Falkenburg et al, 2015 ). When analyzing these data, it looks like the anti-citrullinated Abs are produced due to the ongoing immune response to citrullinated proteins, while RFs appear later and persist due to both the polyclonal and antigen-driven activation of B lymphocytes ( Renaudineau et al, 2005 ).…”

“…When analyzing these data, it looks like the anti-citrullinated Abs are produced due to the ongoing immune response to citrullinated proteins, while RFs appear later and persist due to both the polyclonal and antigen-driven activation of B lymphocytes ( Renaudineau et al, 2005 ). Cambridge et al (2014) , speculated that “in RA, autoreactive B cell specificities escape deletion, receptor editing or anergy early in their development, ultimately giving rise to a population of B cells which can also survive entry into the mature B cell compartment in the periphery.”…”