Fingolimod reduces CXCR4-mediated B cell migration and induces regulatory B cells-mediated anti-inflammatory immune repertoire.

BACKGROUND:Fingolimod, an oral therapy for patients with relapsing Multiple Sclerosis (MS), traps CC chemokine receptor type 7 (CCR7)-expresssing lymphocytes within lymphoid tissues in the periphery, thereby supposedly reducing the infiltration of pathogenic cells into the central nervous system. Additional immunomodulatory effects of Fingolimod, involving cell function, B and T cells interactions and cross-regulation, have scarcely been studied. The objective of this study was to assess how Fingolimod therapy affects B cells functions, namely cell migration, immunoglobullin production and T cell stimulation. METHODS:B cells from 36 patients with relapsing MS were obtained before and after 3 months Fingolimod therapy, while CD4 T cells were collected pre-treatment. Clinical follow-up was performed for 1 year. For in-vitro validation, Lymphoblastoid cell-lines from 16 patients were cultured with Fingolimod. B cell migration towards C-X-C Motif Chemokine Ligand 12 (CXCL12) was assessed using a transwell system. C-X-C chemokine receptor 4 (CXCR4) expression was assessed by flow cytometry and western blot. Plasma immunoglobullins and Brain-derived Neurotrophic Factor (BDNF) were assessed by ELISA or RT-PCR. Drug effect on interacting co-cultured B and T cells on cytokine profiles and T cell proliferation was explored by flow cytometry. RESULTS:Lymphocyte count reduction did not predict clinical response of patients. Fingolimod therapy reduced CXCR4 expression and B cell migration towards CXCL12. No effect was found on immunoglobulins and BDNF. B cells from Fingolimod-treated patients induced a reduction in pro-inflammatory cytokines in T cells, while increased transforming growth factor beta (TGFβ)+ B and T cells, and downregulated IL2-secretion from proliferative T cells. CONCLUSIONS:Fingolimod promotes anti-inflammatory cytokine profiles of B and T cells, through induction of regulatory B cells. Reduced B cell migration capacity in Fingolimod-treated patients leading to decreased cerebral inflammatory infiltration, may be part of the mechanism by which Fingolimod reduces disease activity in MS.