Carter V, LaCava J, Taylor MS, et al. - Researchers undertook a study to examine whether SLE individuals also create autoantibodies against long interspersed nuclear element 1 (LINE-1) p40. Highly purified p40 protein was utilized to quantitate IgG autoantibodies in serum from 172 SLE individuals and from disease controls and age-matched healthy people by immunoblotting and ELISA. In comparison with healthy people, levels were greater in individuals with SLE, but not those with systemic sclerosis. Anti-p40 reactivity was greater in individuals during a flare in contrast with people with disease in remission, associated with the SLE Disease Activity Index score, type I interferon score, lower in complement C3 level, the appearance of anti-DNA antibodies and anti-C1q antibodies, and up to date or previous history of nephritis and associated inversely with age. SLE patient sera also reacted with p40-associated proteins. In summary, autoantibodies reacting with LINE-1 p40 identify a population of SLE individuals with severe and active disease. Moreover, these autoantibodies might express an early immune response against LINE-1 p40 that does not yet by itself suggest clinically notable autoimmunity, however, it might express an early, and still reversible, a step approaching SLE pathogenesis.