Multiple sclerosis (MS) is a disabling, inflammatory, demyelinating disease of the central nervous system considered to be mediated by autoreactive T cells. Dendritic cells (DC), being professional antigen-presenting cells, play a pivotal role in the decision between T-cell activation and anergy. It has been suggested that mature DC (mDC) induce immunity, whereas immature DC (imDC) have the potential to induce tolerance. In this study, we investigated the effects of autologous imDC versus autologous mDC on lymphocytes with respect to the expression of functionally important cell-surface molecules and production of cytokines. Our aims were to investigate whether the maturation status of DC differs between MS and healthy controls (HC) and to explore whether the effects of DC on T-cell responses differ between MS and HC. DC were generated from adherent blood mononuclear cells from patients with MS and HC. imDC were obtained by culture with either granulocyte–macrophage colony-stimulating factor (GM-CSF) + interleukin-4 (IL-4) or GM-CSF + IL-4 + IL-10. mDC were obtained by adding lipopolysaccharide to DC cultures. Upon coculture with autologous lymphocytes, mDC activated the autologous T cells as reflected by increased CD25 and cytotoxic T-lymphocyte antigen-4 expression on CD4+ T cells together with the increased production of both T helper 1 (Th1) (IL-2 and interferon-γ) and Th2 (IL-10 and IL-4) cytokines. Unmodulated naïve imDC induced the production of only IL-4. An exposure of imDC to IL-10 induced the production of IL-4 as well as IL-10 by autologous lymphocytes. We hypothesize that such imDC are important in controlling the proinflammatory environment in vivo in patients with MS.