The kinetics of lymphocyte subset alteration will be monitored in whole-blood samples from all fingolimod- treated patients at the baseline, which will precede the first dose, day 1 and day 7. Mononuclear cells will be isolated from the whole-blood specimens and stained with antibodies to CD4-FITC, CD8-PE, CD19-PerCP, CD56-PE (BD Biosciences, Franklin Lakes, NJ, USA). Data will be acquired using a FACS Caliber (Becton Dickinson Immunocytometry Systems, San Jose, CA, USA) and analyzed with Flow Jo software (Tree Star, Ashland, OR, USA).