Autoimmune response to transthyretin in juvenile idiopathic arthritis
Cristina C. Clement, … , Steven A. Porcelli, Laura Santambrogio
Cristina C. Clement, … , Steven A. Porcelli, Laura Santambrogio
Published February 25, 2016
Citation Information: JCI Insight. 2016;1(2):e85633. https://doi.org/10.1172/jci.insight.85633.
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Research Article Inflammation

Autoimmune response to transthyretin in juvenile idiopathic arthritis

Abstract

Juvenile idiopathic arthritis (JIA) is the most common pediatric rheumatological condition. Although it has been proposed that JIA has an autoimmune component, the autoantigens are still unknown. Using biochemical and proteomic approaches, we identified the molecular chaperone transthyretin (TTR) as an antigenic target for B and T cell immune responses. TTR was eluted from IgG complexes and affinity purified from 3 JIA patients, and a statistically significant increase in TTR autoantibodies was observed in a group of 43 JIA patients. Three cryptic, HLA-DR1–restricted TTR peptides, which induced CD4+ T cell expansion and IFN-γ and TNF-α production in 3 out of 17 analyzed patients, were also identified. Misfolding, aggregation and oxidation of TTR, as observed in the synovial fluid of all JIA patients, enhanced its immunogenicity in HLA-DR1 transgenic mice. Our data point to TTR as an autoantigen potentially involved in the pathogenesis of JIA and to oxidation and aggregation as a mechanism facilitating TTR autoimmunity.

Authors

Cristina C. Clement, Halima Moncrieffe, Aditi Lele, Ginger Janow, Aniuska Becerra, Francesco Bauli, Fawzy A. Saad, Giorgio Perino, Cristina Montagna, Neil Cobelli, John Hardin, Lawrence J. Stern, Norman Ilowite, Steven A. Porcelli, Laura Santambrogio

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Figure 8

HLA-DR1–binding affinity and proliferative response to transthyretin peptides following immunization of HLA-DR1 mice with native, aggregated, or aggregated/oxidized transthyretin.

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HLA-DR1–binding affinity and proliferative response to transthyretin pep...
(A) Inhibition binding curves (percentage bound test peptide vs. test peptide concentration [nM]) for transthyretin (TTR) peptides. Binding to HLA-DR1 molecules measured at 72 hours (1 out of 3 representative experiments is shown). Shown at the top of the graphs are the peptide sequences as well as the calculated values for binding (IC50 [μM]). Binding of the immunodominant viral epitope HA peptide is shown as control. (B) Native gel showing native TTR (monomer at 15 kDa and tetramer at 60 kDa); aggregated TTR, following exposure to low pH; and aggregated and oxidized TTR, following oxidation by Fenton reaction. One out of three gels is shown. (C) T cell–proliferative responses to increasing concentrations of the reported TTR peptides following immunization with native or aggregated or aggregated/oxidized TTR. HLA-DR1 mice were immunized as reported in Methods, popliteal and axillary nodes were harvested 3 weeks later, and T cells were rechallenged in vitro with increasing concentrations of the reported immunogens. Data are reported as stimulation index (BrDu incorporation following antigen stimulation over BrDu incorporation in absence of specific antigen). Data were compiled from 3 separate immunizations (n = 6). Experiments to evaluate T cell proliferation in response to antigen were run in quadruplicate for each antigen concentration tested. Mean ± SD. Data were analyzed by 1-way ANOVA (P < 0.005) and Tukey test. Asterisks indicate statistical significance, calculated at each concentration, between the peptide stimulation index and the native TTR or between the native TTR and the unfolded/carbonylated TTR. *P < 0.05; **P < 0.01; ***P < 0.005; ****P < 0.001.