The ananti-alpha-actinin test completes ananti-DNA determination in systemic lupus erythematosus

In murine systemic lupus erythematosus (SLE) models, nephritogenic anti-dsDNA IgG has been shown to cross-react with a kidney antigen, alpha-actinin, and to be critical in renal pathogenesis. In humans, studies of anti-alpha-actinin antibodies (Abs) are scarce, and these antibodies remain to be evaluated. We have thus far tested sera from patients with SLE (n = 103), rheumatoid arthritis (RA, n = 93), and primary Sjögren syndrome (pSS, n = 34), and from healthy subjects (n = 160), for the presence of anti-alpha-actinin and anti-DNA Abs. The latter were tested using several methods [IIF on Crithidia luciliae (Crit) and ELISA using dsDNA]. Anti-alpha-actinin Abs were confirmed by Western blot. Sera from 23 of 103 SLE patients, 3 of 93 RA patients, 1 of 33 pSS patients, and 1 of 160 controls scored positive for anti-alpha-actinin Abs. In SLE, the positivity was significantly associated with anti-dsDNA reactivity (22 of 23): 19 of 23 sera were alpha-actinin-positive/dsDNA-positive and 13 were alpha-actinin-positive/Crit-positive. Few cases were alpha-actinin-positive/dsDNA-negative: 1 SLE, 3 RA, and 1 control. Furthermore, anti-alpha-actinin Abs have been detected at high level before or at the early stage of lupus nephritis when compared with active and inactive SLE without kidney manifestations.