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

- CX3CL1 levels are increased in the CSF from CIS patients, and in the CSF and serum samples from RRMS patients.
- CX3CR1+, ICAM-1+ and CX3CR1+ICAM-1+ CD4+ cells are enriched in CSF in RRMS patients.
- CX3CL1 upregulates IFN-γ and TNF-α expression by CD4+ cells from RRMS patients.
- CX3CL1 upregulates ICAM-1 expression on CD4+ cells from RRMS patients.
- CX3CL1 induces higher ICAM-1 expression on autoreactive CD4+ cells than antigen alone.

Fractalkine (CX3CL1) levels are increased in the cerebrospinal fluid (CSF) of patients with clinically isolated syndrome (CIS), as well as in the CSF and serum samples from patients with relapsing-remitting multiple sclerosis (RRMS). A higher percentage of circulating CD4+ T-cells expressed its surface receptor (CX3CR1) and intracellular adhesion molecule (ICAM-1) in RRMS patients in comparison to healthy controls (HCs). The CX3CR1+ICAM-1+CD4+ T-cells are enriched in the CSF of the RRMS patients. 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. CX3CL1 significantly increased IFN-γ and TNF-α gene expression and IFN-γ secretion by CD4+ T-cells derived from the RRMS patients. CX3CL1 upregulated ICAM-1 expression on the surface of RRMS patient-derived but not HC-derived CD4+ T-cells. Thus, CX3CL1 induces recruitment of CX3CR1+ICAM-1+CD4+ T-cells into the central nervous system (CNS) during the early inflammatory response in MS.