B cells are increasingly recognized as major players in multiple sclerosis pathogenesis. The BAFF/APRIL system is crucial for B cell homoeostasis and may drive B cell-dependent autoimmunity. We asked whether this system is affected by Interferon (IFN)-beta therapy. We analysed transcription of the ligands (BAFF, APRIL, TWE-PRIL) and the corresponding receptors (BAFF-R, TACI and BCMA) by TaqMan-PCR ex vivo in whole blood and in immune cell subsets purified from IFN-beta-treated multiple sclerosis patients. Serum BAFF concentrations were determined by ELISA. This cross-sectional study involved 107 donors. IFN-beta therapy strongly induced BAFF transcription proportionally to the IFN-beta biomarker MxA in monocytes and granulocytes in vivo. BAFF serum concentrations were elevated in IFN-beta-treated multiple sclerosis patients to a similar level as observed in SLE patients. In cultured PBMC, neutrophils, fibroblasts and astrocytes, BAFF was induced by IFN-beta concentrations similar to those reached in vivo in treated multiple sclerosis patients. BAFF turned out to be the main regulated element of the BAFF/APRIL system. In untreated multiple sclerosis patients, there was no BAFF increase as compared to healthy controls. Our study reveals a complex situation. We show that IFN-beta therapy induces a potent B cell survival factor, BAFF. However, B cell depletion would be desirable at least in some multiple sclerosis patients. The systemic induction of BAFF by IFN-beta therapy may facilitate the production of various autoantibodies and of IFN-neutralizing antibodies. Individual MS/NMO patients who have major B cell involvement may benefit less than others from IFN-beta therapy, thus explaining interindividual differences of the therapeutic response.

Natalizumab (NAT) is an effective therapy for relapsing-remitting multiple sclerosis (MS), but is associated with an increased risk of progressive multifocal leucoencephalopathy after 2 years therapy. Thus, NAT treated patients often decide to stop NAT therapy after 2 years. Reports on recurrence of disease activity after NAT discontinuation are controversial. We studied disease activity in 13 MS patients who stopped NAT therapy and either remained without disease modifying therapy (no DMT, n = 6), or switched to glatiramer acetate (GLAT, n = 7). Annual relapse rate (ARR), expanded disability status scale (EDSS), and number of patients with contrast-enhancing-lesions (Gd+) on MRI before, during and within 1 year after NAT were determined. We observed recurrence of disease activity in both groups (5/7 GLAT treated patients and 6/6 patients without DMT) within 12 months after cessation of NAT (mean time to first relapse was 5.5 months for all patients). One of the GLAT treated patients and three patients without DMT had severe relapses with sustained EDSS worsening. No differences in ARR, EDSS and MRI parameters were seen between both groups. Patients with relapses after NAT therapy, however, tended to show higher disease activity (EDSS, ARR) before initiation of NAT therapy compared to patients without relapses. Duration of NAT treatment was not associated with higher disease activity after NAT discontinuation. In this observation the majority of patients showed reappearance of disease activity after discontinuation of NAT regardless of whether they switched to GLAT or remained without DMT. Further treatment strategies are warranted for patients who discontinue NAT therapy.

BackgroundFingolimod (FTY720) is the first sphingosine-1-phosphate (S1P) receptor modulator approved for the treatment of multiple sclerosis. The phosphorylated active metabolite FTY720-phosphate (FTY-P) interferes with lymphocyte trafficking. In addition, it accumulates in the CNS and reduces brain atrophy in multiple sclerosis (MS), and neuroprotective effects are hypothesized.MethodsHuman primary astrocytes as well as human astrocytoma cells were stimulated with FTY-P or S1P. We analyzed gene expression by a genome-wide microarray and validated induced candidate genes by quantitative PCR (qPCR) and ELISA. To identify the S1P-receptor subtypes involved, we applied a membrane-impermeable S1P analog (dihydro-S1P), receptor subtype specific agonists and antagonists, as well as RNAi silencing.ResultsFTY-P induced leukemia inhibitory factor (LIF), interleukin 11 (IL11), and heparin-binding EGF-like growth factor (HBEGF) mRNA, as well as secretion of LIF and IL11 protein. In order to mimic an inflammatory milieu as observed in active MS lesions, we combined FTY-P application with tumor necrosis factor (TNF). In the presence of this key inflammatory cytokine, FTY-P synergistically induced LIF, HBEGF, and IL11 mRNA, as well as secretion of LIF and IL11 protein. TNF itself induced inflammatory, B-cell promoting, and antiviral factors (CXCL10, BAFF, MX1, and OAS2). Their induction was blocked by FTY-P. After continuous exposure of cells to FTY-P or S1P for up to 7 days, the extent of induction of neurotrophic factors and the suppression of TNF-induced inflammatory genes declined but was still detectable. The induction of neurotrophic factors was mediated via surface S1P receptors 1 (S1PR1) and 3 (S1PR3).ConclusionsWe identified effects of FTY-P on astrocytes, namely induction of neurotrophic mediators (LIF, HBEGF, and IL11) and inhibition of TNF-induced inflammatory genes (CXCL10, BAFF, MX1, and OAS2). This supports the view that a part of the effects of fingolimod may be mediated via astrocytes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0393-6) contains supplementary material, which is available to authorized users.

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