IgM antibodies against acetylated proteins as a possible starting point of the anti-modified protein antibody response in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterised by the presence of anti-modified protein antibodies (AMPA): anti-citrullinated protein antibodies (ACPA), anti-carbamylated protein antibodies (anti-CarP) and anti-acetylated protein antibodies (AAPA).These AMPA responses are specific for RA and have consistently been found to develop years before disease onset. 1 2 Most studies on AMPA in (pre-disease) RA are focused on IgG antibodies.However, IgM is the first isotype generated in (auto)antibody responses.It is unclear whether IgM autoimmunity differs Bibl.