Enhanced NETosis in circulating and synovial fluid RA neutrophils may be impacted by inflammatory cytokines such as IL-17 and TNF-α as well as the presence of ACPAs.1,28 Research by Sohn et al.10 demonstrated that immune complexes (ICs) containing NET-derived citrullinated H2B from the RA synovium both activate macrophage TNF-α production and propagate NETosis in vitro, as well as induce ACPA-associated arthritis in a mouse model in vivo. Here, H2BC21 is linked to rheumatoid arthritis.