Background The aim of this study was to evaluate the prevalence and clinical significance of Anti-neuronal antibodies (AnAb) in a cohort of neuropsychiatric (NP) Systemic Lupus Erythematosus (SLE) patients.

Methods Overall, 28 SLE patients (age 45.6 ± 14.4 years) with inflammatory neuropsychiatric syndromes, classified according to existing criteria (1, 2) were enrolled and serum samples were collected before starting treatment for the specific NP event; 41 consecutive SLE patients (44.2 ± 14.2 years) without NP involvement, 22 Multiple Sclerosis patients (37.9 ± 11.0 years) and 82 healthy subjects (44.8 ± 15.0 years) served as controls. Search for AnAb was performed by tissue-based immunohistochemistry assays (IHC) on male Sprague Dawley rat’s brain sections and confirmed by cell-based immunocytochemistry assays on SH-SY5Y (human neuroblastoma) cell cultures. The association between serum positivity for AnAb by IHC and a large panel of data (demographic, serologic, SLEDAI, conventional brain MRI, treatment) was investigated by univariate analysis. Multivariate models were fitted with covariates with p<0.05 to identify factors independently associated with serum positivity for AnAb; p<0.05 were considered statistically significant.

Results AnAb were detected in 23 (82.1%) NPSLE patients and in 16 (39.0%) SLE patients without NP involvement resulting in 82% specificity (95%CI 71%-90%) and 61% sensitivity (95%CI 48%-72%) in differentiating NPSLE from SLE without NP involvement. None of the sera from MS patients (0%) and healthy subjects (0%) showed AnAb. Serum AnAb by IHC were independently associated with NPSLE (p<0.01) and higher SLEDAI (p<0.01). No association with specific NPSLE syndrome and brain conventional MRI abnormalities was identified.

Conclusion AnAb are significantly more frequent in patients with NPSLE than SLE. Further studies are needed to identify the unknown neuronal antigens targeted by AnAb in SLE patients.