Our previous studies indicate that EBI is involved in

Our previous studies indicate that EBI2 is involved in the regulation of pro-inflammatory responses and inter-cellular communication under pathophysiological conditions such as LPS challenge (Rutkowska et al., 2016b). The data showed that media taken from LPS stimulated astrocytes induces macrophage migration (Rutkowska et al., 2016b). Moreover, other research has shown that mice deficient in CH25H enzyme cannot synthesise oxysterol 25HC and show aggravated course of EAE (Reboldi et al., 2014). In the same study, CH25H deficient mouse LY2940680 released greater amounts of IL1β after LPS stimulation than their wild type counterparts, suggesting that 25HC has anti-inflammatory properties (Reboldi et al., 2014). In line with these results, here the in vivo data showed that EBI2 KO mice challenged with LPS release greater amounts of pro-inflammatory cytokines such as IL6, TNFα and KCGRO than wild-type mice. These results support further a role for EBI2 in the regulation of pro-inflammatory cytokine signalling in the CNS.
Funding This work was supported by Irish Research Council (IRC) - Enterprise Partnership Scheme (EPS), Novartis Pharma, Basel, Switzerland. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 665778. National Science Centre, Poland, fellowship registration number POLONEZ 2: 2016/21/P/NZ3/00897.
Disclosure/conflict of interest
Acknowledgments
Introduction Multiple sclerosis (MS) is a frequent chronic inflammatory disease of the CNS leading to neurologic disability and lifelong morbidity in young adults (Compston and Coles, 2002). Despite advances in MS research, its pathophysiology is still far from being well understood, so it remains an incurable disease. In addition, many patients still do not respond appropriately to available drugs or experience heavy side effects. Inflammation in MS involves circulating auto-reactive T cells, which escape immune regulation and enter the brain, resulting in inflammatory infiltrates and demyelination throughout the CNS (Compston and Coles, 2002). Thus, immune cell migration is a key point in the disease process (Engelhardt and Ransohoff, 2012). Subsets of oxidized cholesterol metabolites, oxysterols, were reported to play a role in inflammation and immune cell chemotactism (Bauman et al., 2009, Yi et al., 2012). More precisely, the oxysterol 7α,25-dihydroxycholesterol (7α,25-OHC), synthesized through the enzymes cholesterol 25-hydroxylase and 25-hydroxycholesterol 7-alpha-hydroxylase, was characterized as having peculiar chemotactic properties by being the strongest ligand activating the Epstein-Barr virus-induced gene 2 (EBI2) receptor (Hannedouche et al., 2011, Liu et al., 2011). The expression of this receptor is well characterized on murine immune cells and found to be maximal on mature B cells and CD4+ T cells, including T follicular helper (Tfh) cells, but is also described on dendritic cells (DC) and plasmacytoid DCs (pDCs) (Chiang et al., 2013, Gatto et al., 2013, Li et al., 2016, Pereira et al., 2009, Suan et al., 2015). In vivo, EBI2 activation was reported to direct B and Tfh cell positioning in follicles and osteoclasts migration toward bone surface (Gatto et al., 2009, Kelly et al., 2011, Li et al., 2016, Nevius et al., 2015, Pereira et al., 2009, Suan et al., 2015, Yi et al., 2012). We showed that EBI2 promoted memory CD44+CD4+ T cell, particularly interleukin (IL)-17-secreting T cell, and migration during experimental autoimmune encephalomyelitis (EAE) (Chalmin et al., 2015). In human, EBI2 is further expressed and promotes the in vitro migration of astrocytes and macrophages (Eibinger et al., 2013, Preuss et al., 2014, Rutkowska et al., 2015). However, the expression and the function of EBI2 in human lymphocytes are scarcely studied, while EBI2’s potential role in MS and the impact of disease-modifying treatments (DMTs) on this receptor biology have not been examined. In this study, we aimed to characterize the expression and function of EBI2 in human peripheral blood lymphocytes by using flow cytometry and an in vitro migration assay. We tested lymphocytes obtained from healthy donors (HDs) and relapsing-remitting multiple sclerosis (RRMS) patients who were either untreated or receiving a DMT, in particular natalizumab, a humanized monoclonal immunoglobulin G4 (IgG4) (Börnsen et al., 2012) antibody blocking the α4-integrin subunit and thus interfering with leukocytes migration to the CNS (Engelhardt and Kappos, 2008).