PRTN3 and rheumatoid arthritis: The precision of these measurements was assessed for a subset of three RA patients regarding total ACPA IgG signals (Figure S2a, Supporting Information) as well as total/ACPA IgG allotype distributions (Figure S2b, Supporting Information) and glycosylation patterns of IgG1 and IgG4 of ACPA (Figure S3, Supporting Information) and total IgG (Figure S4, Supporting Information).