Anti-cardiolipin antibodies in neurological disorders: cross-reaction with anti-single stranded DNA activity

Antiphospholipid (PL) antibodies have been detected in sera from patients with chronic neurological diseases associated with disorders of immunity. In an isotype specific radioimmunoassay for anti-cardiolipin (CL) antibodies, we found IgM anti-CL (greater than 2 s.d. above mean of controls) in 17/25 (68%) patients with myasthenia gravis (MG), 8/25 (32%) with the Lambert-Eaton myasthenic syndrome (LEMS), 5/17 (29%) with multiple sclerosis and 3/11 (27%) cases of migraine. IgG anti-CL was only found in low titres in sera from 10 patients with MG and three with LEMS. Significant anti-CL activity could not be detected in sera from nine patients with acute Guillain-Barre Syndrome (GBS), 12 chronic cases of epilepsy, 8/9 with oat cell carcinoma and 9/10 with acute stroke. Further tests on 39 sera with the highest anti-CL activity, from all of the above disease groups, showed a significant correlation between IgM anti-CL and IgM anti-ss DNA activities. In a series of competitive inhibition assays six sera from patients with MG were shown to have a proportion of both specific and cross-reactive IgM anti-CL and IgM anti-ss DNA antibodies. Anti-phospholipid antibodies occur in certain neurological diseases, at lower titres than seen in SLE, yet their cross-reactive binding to ss DNA suggests similar antibacterial origins as have been proposed for lupus auto-antibodies. In the absence of overt infection they might reflect a breakdown of tolerance for non-organ specific membrane antigens in diseases with predominantly organ specific membrane bound putative autoimmunogens.