Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease characterized by leukocyte infiltration into the central nervous system (CNS). Migration of lymphocyte subpopulations towards CXCL12 was analyzed coupled to six-color flow cytometry in untreated patients in the remitting phase, during relapse, in patients with clinically isolated syndrome (CIS), and in healthy volunteers. Significantly higher migration rates of natural killer cells (CD45+CD3-CD16/56+) were observed in patients in remission and CIS patients than in patients during relapse and in controls. Moreover, the frequency of CD3-CD16/56+CXCR4+ cells is higher in patients in remission and in CIS patients, but not during relapse. (C) 2015 Elsevier B.V. All rights reserved.