Relapsing–remitting multiple sclerosis (RRMS) is a complex autoimmune disease of the central nervous system with oscillating phases of relapse and remission. RRMS has been considered to be driven by T helper type 1 (Th1) lymphocytes but new data indicate the involvement of Th17 responses. In the present study, blood samples from patients (n = 48) and healthy individuals (n = 44) were evaluated for their immunological status. T cells from patients with RRMS expressed high levels of the activation marker CD28 (P < 0·05) and secreted both interferon-γ (CD8: P < 0·05) and interleukin-17 upon polyclonal mitogen or myelin oligodendrocyte glycoprotein antigen stimulation. However, T cells from patients with RRMS in remission, in contrast to relapse, had poor proliferative capacity (P < 0·05) suggesting that they are controlled and kept in anergy. This anergy could be broken with CD28 stimulation that restored the T-cell replication. Furthermore, the patients with RRMS had normal levels of CD4+ Foxp3+ T regulatory cells but the frequency of Foxp3+ cells lacking CD127 (interleukin-7 receptor) was lower in patients with MS (mean 12%) compared to healthy controls (mean 29%). Still, regulatory cells (CD25+ sorted cells) from patients with RRMS displayed no difference in suppressive capacity. In conclusion, patients in relapse/remission demonstrate in vitro T-cell responses that are both Th1 and Th17 that, while in remission, appear to be controlled by tolerogenic mechanisms yet to be investigated.