Antibodies to microtubule-associated protein-2 in the cerebrospinal fluid are a useful diagnostic biomarker for neuropsychiatric systemic lupus erythematosus.

OBJECTIVE: Previous reports indicate that serum anti-microtubule-associated protein 2 (MAP-2) antibodies are common in sera from patients with neuropsychiatric systemic lupus erythematosus (NPSLE). Differential diagnosis of NPSLE is occasionally difficult because of differential diagnosis which can mimic NPSLE. Therefore, specific biomarkers for NPSLE are needed. We conducted this study to clarify whether cerebrospinal fluid (CSF) anti-MAP-2 antibodies are a useful diagnostic biomarker for NPSLE. METHODS: Enzyme-linked immunosorbent assay was conducted to measure CSF concentrations of anti-MAP-2 and anti-ribosomal P antibodies and of IL-6 in NPSLE patients (n = 24) and non-NPSLE controls (n = 17). The non-NPSLE controls consisted of systemic lupus erythematosus patients with neuropsychiatric symptoms caused by non-NPSLE conditions (n = 10) and patients with other connective tissue diseases (n = 7). RESULTS: Significantly higher anti-MAP-2 antibody titers were found in the CSF of patients with NPSLE versus non-NPSLE controls. The prevalence of anti-MAP-2 antibodies was 33.3% (8/24) in NPSLE patients when a positive cutoff value was 3 standard deviations above the mean optical density of non-NPSLE controls. None of the controls had anti-MAP-2 antibodies in their CSF. Both anti-ribosomal P antibody titers and concentration of IL-6 in the CSF were significantly higher in patients with NPSLE having anti-MAP-2 antibodies than in patients with non-NPSLE controls. CONCLUSION: Anti-MAP-2 antibodies could be detected in the CSF of 33.3% of patients with NPSLE, and its presence was highly specific for NPSLE. We propose that CSF anti-MAP-2 antibodies are a novel and useful diagnostic biomarker for NPSLE.