Fig. 1

Prevalence of the IgG, IgM, and IgA (sub)classes within anti-UH-RA.1 antibodies and anti-UH-RA.21 antibodies. a Anti-UH-RA.1 and d anti-UH-RA.21 antibodies of the IgG, IgM, and IgA isotypes. b and e With cutoffs based on HC reactivity and set to 90 % RA specificity, the proportion of IgG, IgM, and IgA was similar in patients with RA and RC for antibodies against UH-RA.1 and UH-RA.21. c Subtyping of IgG-positive patients for IgG1–IgG4 pointed toward IgG3 as the dominant subclass within anti-UH-RA.1 antibodies in all patient and control groups. Anti-UH-RA.1-IgG1 and anti- UH-RA.1-IgG2 were RA-specific but less prevalent. No anti-UH-RA.1 antibodies of the IgG4 isotype were detected. f Regarding anti-UH-RA.21, IgG was represented mostly by IgG2, followed by IgG3 and IgG1. The latter two were less prevalent but not found in HC. Anti-UH-RA.21 antibodies of the IgG4 isotype were detected in one patient with RA. Bars represent the proportion of the respective isotype to the total antibody reactivity. Sums of individual proportions within the same patient group can exceed 100 % because patients can carry more than one (sub)class. HC healthy control subjects, Ig immunoglobulin, RA rheumatoid arthritis, RC rheumatic control subjects