Although the literature contains conflicting data regarding the nature and prevalence of anti-neutrophil-binding IgG in RA depending on the method used for analysis of antigenic targets,33,34,37,38 it is estimated that IgG-containing ICs as well as complement C3 activation fragments can be found in the joints of >90% of RA patients.39,40. Here, C3 is linked to rheumatoid arthritis.