Anti-histone reactivity in systemic lupus erythematosus sera: a disease activity index linked to the presence of DNA:anti-DNA immune complexes

Predictive value of autoantibodies for activity of systemic lupus erythematosus

There is no serologic test that reliably measures disease activity in systemic lupus erythematosus (SLE). The ‘gold standard’ is the anti-dsDNA antibody test, which has been used as a marker of disease activity by clinicians in SLE for over 35 years. Anti-dsDNA antibodies perform best in those with lupus nephritis, specifically in the presence of a proliferative lesion [World Health Organization (WHO) class III or IV] on renal biopsy. In one recent meta-analysis, the mean positivelikelihood ratio of anti-dsDNA antibodies as a marker of disease activity in SLE was 4.14, implying the overall predictive effect was small. More recently autoantibodyassays have been developed that show greater promise in gauging SLE disease activity, specifically anti-nucleosome and anti-C1q antibodies (especially with renal disease activity). Other tests thought previously to be lacking in specificity that refinements in ELISA technology now render possibly useful include anti-heparan sulfate, anti-ssDNA and anti-Scl-70 autoantibodies. Other tests that as yet have not been shown to be as reliable (and therefore are not as useful in clinical practice for serial determinationto measure disease activity) include other anti-extractablenuclear antibodies (anti-Ro, La, Sm, RNP), anti-cardiolipinantibodies, and anti-nuclear cytoplasmic antibodies (ANCA). New technologies using proteomic determinations show promise as aids in the search for more reliable and feasible autoantibody determinations of disease activity in SLE.

Anti-histones antibodies in systemic lupus erythematosus: prevalence and frequency in neuropsychiatric lupus

To investigate the specificity, sensitivity, and concomitant presence of antibodies against histones (H), histone H1 (H1), and histone H3 (H3) in patients with systemic lupus erythematosus (SLE) and analyze their association with SLE. Serum IgG anti-histones antibodies were detected by enzyme-linked immunosorbent assay in 144 SLE patients consisting of 24 neuropsychiatric lupus (NPSLE), 65 lupus nephritis (LN), and 55 SLE, 100 other rheumatic diseases patients, as well as 40 healthy controls. Clinical and biological parameters of the patients were also evaluated. Anti-H, anti-H1, and anti-H3 antibodies yielded a sensitivity of approximately 33% and a specificity of more than 93% for SLE, which was comparable to that found for anti-double-stranded DNA (anti-dsDNa) antibodies. More significantly, anti-histone antibody is found in approximately 50% of patients with NPSLE compared with LN. Moreover, the titers of anti-histones antibodies of NPSLE patients were significantly higher than that of patients with SLE and LN. The sequential analysis revealed a close correlation of anti-H and anti-H1 antibodies with SLE disease activity. There was an approximate 30% positive rate of anti-histones antibodies in 144 SLE patients lacking anti-nucleosome, anti-mDNA, anti-Sm, and anti-dsDNA antibodies. Antibodies to histones H1 and H3 are markers with high specificity of 93.6-96.4% for SLE. The anti-histone antibody markers are prevalent in approximately 50% of NPSLE. Furthermore, there was a strong correlation with SLE disease activity index and levels of antibodies to histones and H1.

A subset of lupus anti-DNA antibodies cross-reacts with the NR2 glutamate receptor in systemic lupus erythematosus

In systemic lupus erythematosus, antibodies against double-stranded DNA are a major contributor to renal disease. We have previously demonstrated that the pentapeptide Asp/Glu-Trp-Asp/Glu-Tyr-Ser/Gly is a molecular mimic of double-stranded DNA. This sequence is also present in the extracellular domain of murine and human NMDA (N-methyl-D-aspartate) receptor subunits NR2a and NR2b. Here we show that the NR2 receptor is recognized by both murine and human anti-DNA antibodies. Moreover, anti-DNA antibodies with this cross-reactivity mediate apoptotic death of neurons in vivo and in vitro. Finally, we show that the cerebrospinal fluid of a patient with systemic lupus erythematosus contains these antibodies and also mediates neuronal death via an apoptotic pathway. These observations indicate that lupus antibodies cross-react with DNA and NMDA receptors, gain access to cerebrospinal fluid and may mediate non-thrombotic and non-vasculitic abnormalities of the central nervous system.