The latter is mainly mediated by proteases and ROS-producing enzymes like NADPH oxidase (O2•- generation) and myeloperoxidase (MPO, HOCl production) [6,9,10] which are released by pro-inflammatory stimulated neutrophils [11].PMNs also play manifold roles in the chronification of RA [12–14]: The solidification of the disease includes autoimmune aspects as evidenced by the fact that B cell-derived rheumatoid factors (antibodies against the Fc part of IgG antibodies) and antibodies against citrullinated proteins are key markers of its pathogenesis [1,2,15]. The gene discussed is MPO; the disease is rheumatoid arthritis.