Cerebrospinal fluid levels of a proliferation-inducing ligand (APRIL) are increased in patients with neuropsychiatric systemic lupus erythematosus

Abstract

Objectives: A proliferation-inducing ligand (APRIL) and B-cell activation factor (BAFF) are B-cell stimulation and survival molecules. We have investigated whether APRIL and/or BAFF activity is enhanced in the systemic and/or intrathechal compartment of patients with neuropsychiatric systemic lupus erythematosus (NPSLE). In particular, the association between fatigue and APRIL/BAFF activity was investigated.

Methods: Twenty-eight NPSLE patients were evaluated clinically, with sampling of cerebrospinal fluid (CSF) and blood, and magnetic resonance imaging (MRI). CSF and blood samples from 13 multiple sclerosis (MS) patients and 17 patients with other neurological diseases (OND) were used as controls. Protein levels of BAFF and APRIL were quantified in CSF and plasma, mRNA expression levels of BAFF and APRIL were determined in peripheral blood (PBMC) and CSF mononuclear cells (CSF-MC). The Fatigue Severity Scale (FSS) was used to quantify the degree of fatigue.

Results: NPSLE patients had higher levels of APRIL in CSF as compared to OND (p < 0.01). No corresponding increase in APRIL mRNA levels was detected in CSF-MC. BAFF levels in plasma were higher in NPSLE than in OND (p < 0.001). BAFF mRNA expression in PBMC was also higher in NPSLE patients than in controls (p < 0.05). FSS scores in patients with NPSLE correlated significantly with APRIL levels in CSF.

Conclusions: Protein levels of APRIL in CSF were increased in NPSLE as compared to OND. Moreover, there was a positive correlation between CSF APRIL levels and fatigue. Our results suggest that APRIL and possibly also BAFF may be involved in the pathogenesis of NPSLE and in SLE-related fatigue.

Acknowledgements

We thank Rosmarie Johnson for excellent assistance in collecting patient samples and Dr Fredrik Piehl for critical review of the manuscript. This work was supported by K.I. Fonder, NHR, King Gustaf V’s 80th Birthday Fund, the Swedish Society of Medicine, the Swedish Rheumatism Association, the Centre of Gender-related Medicine at Karolinska Institutet, the Swedish Heart–Lung Foundation, the Åke Wiberg Foundation, and Axel and Eva Wallström’s Foundation.