The role of fractalkine (CX3CL1) in regulation of CD4+ cell migration to the central nervous system in patients with relapsing-remitting multiple sclerosis (S12.003)

OBJECTIVE: To characterize the role of fractalkine (CX3CL1) in the early migration of autoreactive CD4+ cells to the CNS of patients with relapsing remitting multiple sclerosis (RRMS). BACKGROUND: Our previous work has identified that CD4+CD28- cells, which are expanded in RRMS patients and are enriched for cells reactive to myelin basic protein (MBP), preferentially express CX3CL1 receptor CX3CR1. DESIGN/METHODS: 53 untreated RRMS, 10 clinically isolated syndrome (CIS) patients and 64 control individuals were enrolled in the study. Cerebrospinal fluid (CSF) and blood samples were used to identify the expression of inflammatory proteins using protein array (RayBIotech) and ELISA. FACS was used to determine the expression of CXCR1 and adhesion molecules. Cytokine gene and ICAM-1 surface expression was determined in CD4 cells upon stimulation with CX3CL1. RESULTS: CSF CX3CL1 concentrations are elevated in CIS patients. A higher percentage of CD4+ T-cells from peripheral circulation expressed CX3CR1 and intracellular adhesion molecule (ICAM-1) in the RRMS patients in comparison to the healthy controls (HCs). The CX3CR1+ICAM-1+CD4+ T-cells are enriched in the CSF of the RRMS patients in comparison to their matched blood samples. In-vitro migration studies revealed that CD4+ T-cells which migrated toward a CX3CL1 gradient expressed higher levels of ICAM-1 than non-migrating cells. In studies examining the mechanisms by which CX3CL1 induces T-cell migration, we demonstrated that CX3CL1 significantly increased IFN-γ and TNF-α gene expression and IFN-γ secretion by CD4+ T-cells derived from RRMS patients, but not from HCs. CX3CL1 upregulated ICAM-1 expression on the surface of RRMS patient-derived but not HC-derived CD4+ T-cells and it increased ICAM-1 expression on stimulated myelin antigen-specific CD4+ T-cell lines above the levels induced by myelin antigen stimulation. CONCLUSIONS: CX3CL1 induces proinflammatory cytokine secretion, expression of ICAM-1, and recruitment of CX3CR1+ICAM-1+CD4+ T-cells into the CNS during the early inflammatory response in MS. Study Supported by: NMSS. Disclosure: Dr. Markovic has received personal compensation for activities with EMD Serono. Dr. Markovic has received research support from Biogen Idec, EMD Serono, Genzyme, and Novartis. Dr. Blauth has nothing to disclose. Dr. Zhang has received personal compensation for activities with EMD Serono. Dr. Chopra has nothing to disclose.