Macrophage extracellular traps require peptidylarginine deiminase 2 and 4 and are a source of citrullinated antigens bound by rheumatoid arthritis autoantibodies

Abstract Anti-citrullinated protein antibodies (ACPAs) are a hallmark of rheumatoid arthritis, but the sources citrullinated antigens remain incompletely defined. Neutrophil extracellular traps (NETs) appear to be source ACPA targets. However, while citrullinating enzyme peptidylarginine deiminase (PAD)4 is required for producing NETs, it not citrullination in murine arthritis. Conversely, PAD2 has limited role NETs major contributor proteins. Thus, additional likely exist. We investigated if macrophage (METs) could proteins or PAD4 dependent manner. Thioglycolate induced macrophages from wild-type, −/−and −/−mice were activated with variety stimulants, then fixed and stained DAPI either anti-citrullinated histone H4 (H4C3) antibody sera ACPA+ ACPA− arthritis subjects. METs visualized by immunofluorescence, confirmed using DNase, counted blinded manner, compared paired-T test. found that ionomycin monosodium urate (MSU) crystals induce (H4C3 stained). In absence PAD4, reduced response MSU when wildtype, complete −/−macrophages. Also, IgG sera, bound METs. Finally, MSU. contribute generation targeted ACPAs PAD2− PAD4-dependent Funding this work was provided U.S. Army MedicalResearch Acquisition Activity through Peer Reviewed Program (W81XWH-18-1-0717) M.A.S.