Fig. 1
Anti-CarP antibody isotypes and IgG subclasses are present in RA sera. ELISAs were performed to detect anti-carbamylated protein (anti-CarP) antibody isotypes (a) and immunoglobulin G (IgG) subclasses (b) in sera of 196 healthy controls (HC) and 373 rheumatoid arthritis (RA) patients. The mean (red line) plus two times the standard deviation in HC was established as the cut-off for the anti-CarP antibody isotypes. The 97th percentile in HC was used as the cut-off for the IgG subclasses. The dotted line represents the cut-off. The specific anti-CarP reactivity is depicted in arbitrary units (AU) per millilitre. The number of samples tested and the percentage positivity is shown below the graphs. c Percentage positivity of anti-CarP antibody isotypes and IgG subclasses in all RA patients (grey bars, n = 373), anti-citrullinated protein antibody (ACPA) IgG-positive RA patients (dark grey bars, n = 217), ACPA IgG-negative RA patients (black bars, n = 156), and HC (light grey bars, n = 196)