SUMMARY
Malondialdehyde (MDA), a peroxidative end‐product released during polyunsaturated fatty acid degradation, reacts strongly with lysine residues of cellular proteins. MDA‐modified proteins become immunogenic and may elicit specific autoantibody formation. We hypothesized that systemic diseases in which inflammatory events occur, could be an interesting model for studying oxidative stress. A few studies have suggested that MDA‐modified proteins may exist in systemic diseases, and that autoantibodies to MDA‐modified structures might reflect this oxidative process. Autoantibodies to MDA‐modified epitope(s) were therefore assayed in sera of patients with systemic lupus erythematosus (SLE, n = 29), scleroderma (SCL, n = 11), giant cell arteritis (GCA, n = 11), periarteritis nodosa (PAN, n = 10), rheumatoid arthritis (RA, n = 9), and healthy subjects (HS, n = 32). Significantly increased anti‐MDA‐modified epitope(s) autoantibodies were found in patients with SLE and also in other systemic diseases such as PAN and SCL. Autoantibodies to MDA‐modified epitope(s) were predominantly of IgM isotype, with low levels of IgG and no IgA activity. In SLE, anti‐MDA‐modified epitope(s) autoantibody titres correlated strongly with systemic lupus activity measure (SLAM, r = 0·702, P = 0·0001), anti‐nuclear antigen autoantibodies (ANA, r = 0·4, P = 0·029), IgG anti‐cardiolipin (r = 0·558, P = 0·03) and the steroid drug regimen (r = 0·52, P = 0·004). Autoantibodies to MDA‐modified epitope(s) may reflect oxidative modifications occurring in systemic diseases, and might be useful as clinical markers of SLE activity if further investigated.
