Table 1.
Candidate autoantigens specifically bound to ACPA*.
Fig 1.
Reactivity to citrullinated histone H4 peptides in synovial fluids.
Synthetic H4 peptides containing citrulline (Cit3, Cit17, Cit19, Cit39, Cit40, and Cit95) and control peptide (Pc) were coated to ELISA microplates, respectively, at 2.5 μg/well and blocked by BSA. Synovial fluids from anti-CCP3 positive RA (n = 34) and anti-CCP3 negative arthritis (n = 24) were tested for the levels of ACPA against each particular peptide. The mean value in each group is marked by a bar. The p-value was determined by comparing mean reactivity levels for each citrullinated peptide to the control peptide using t-test.
Fig 2.
Reactivity to citrullinated histone H4 peptides in anti-CCP3 positive and negative sera.
Sera from anti-CCP3 positive RA (n = 54) and anti-CCP3 negative healthy controls (n = 24) were tested for reactivity toward a number of citrullinated peptides derived from histone H4 (Cit19, Cit39, Cit40, Cit39-40), and control peptide (Pc). The p-value was determined by comparing mean reactivity levels for each citrullinated peptide to the control peptide using t-test.
Fig 3.
Reactivity to the histone H4 Cit39-40 peptide in a spectrum of ACPA positive and ACPA negative sera.
Sera from anti-CCP3 positive Indigenous North American (INA) RA patients (n = 90), anti-CCP3 negative INA RA (n = 40), anti-CCP3 positive INA FDR (n = 26), anti-CCP3 negative INA FDR (n = 53), unrelated healthy INA controls (n = 54), anti-CCP3 positive Caucasian RA patients (n = 78), anti-CCP3 negative Caucasian RA patients (n = 38), and healthy Caucasian controls (n = 26), were tested for reactivity towards the citrullinated H4 Cit39-40 peptide. Mean levels of reactivity toward the Cit39-40 peptide were compared between anti-CCP3 positive and negative individuals in each group, and p-values represent significant differences as determined by t-test.
Fig 4.
Histone H4 Cit39-40 peptide competitively inhibits anti-CCP3 reactivity in synovial fluid and serum.
Equal volumes of anti-CCP3 positive synovial fluids (n = 35) and sera (n = 44) were premixed with 50mM of either a control peptide (Pc), peptide Cit19, peptide Cit39-40, or PBS for 20 minutes. These premixed samples were then tested for their anti-CCP3 reactivity. The ratio of each peptide treated sample to the PBS treated sample was used to calculate percentage inhibition. A) synovial fluid; B) serum. The p-value represents a significant difference between an H4 peptide and the Pc, using t-test.