Cytotoxic and immunomodulatory effects of cladribine on T cells from naïve RRMS patients were studied by tracking changes in phenotypic markers of aggressivity, such as the T cell surface markers CXCR3, CCR6 and CD161, as well as the secretion of IFNγ and IL17. This evidence concerns the gene IL17A and relapsing-remitting multiple sclerosis.