England BR, et al. - Anti–malondialdehyde–acetaldehyde (anti-MAA) antibody (IgA, IgM, IgG) concentrations were measured in cases with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) by the researchers in order to contrast serum anti-MAA antibody levels and MAA expression in lung tissue from subjects with RA-ILD to those obtained in controls. Ninety out of 1,823 RA cases had prevalent RA-ILD. In RA-ILD, serum IgA and IgM anti-MAA antibody concentrations were higher vs RA with chronic obstructive pulmonary disease or RA alone. The highest quartiles of IgA anti-MAA antibody concentration and IgM were significantly correlated with the presence of RA-ILD, after adjustment for covariates. From all other groups, MAA expression in RA-ILD lung tissue was greater than in tissue which colocalized with citrulline, CD19+ B cells, and extracellular matrix proteins to the greatest degree in RA-ILD. Hence, among RA subjects, serum IgA and IgM anti-MAA antibody were correlated with ILD. Moreover, MAA was highly expressed in RA-ILD lung tissue, where it colocalized with other RA autoantigens, autoreactive B cells, and extracellular matrix proteins, reflecting its potential role in the pathogenesis of RA-ILD.