Dendritic cell vaccine design: Strategies for eliciting peripheral tolerance as therapy of autoimmune diseases

Dendritic cells (DC), as potent antigen-presenting cells (APC), constitute a complex system of cells that initiate and regulate immune responses that result in two opposite outcomes: immunity or tolerance. The fine regulation of these two distinct functions is not completely understood. After loading with antigen, DC exhibit the properties of both antigen and adjuvant, the functional components of vaccines. For a long time, attention has focused on the exceptional ability of DC as professional APC capable of eliciting T and B cell-mediated responses, and on their potential as immunotherapy in cancer. DC exhibit both heterogeneity and plasticity. On the one hand, distinct DC subsets exhibit distinct functions. On the other hand, DC functions can be altered by the cytokine environment or other factors. There is increasing evidence that DC could be used as a tool to induce peripheral tolerance. Because DC-based immunotherapy in autoimmune diseases depends on tolerogenic DC, discerning markers for tolerogenic DC is of great importance. Immature DC, plasmacytoid DC and interleukin-10-modified DC can mediate immune tolerance by inducing T-cell anergy or T-helper type 2 responses. Several possibilities exist for rational modulation of DC to achieve therapeutic tolerance against autoimmune diseases. The final goal is to create optimal prerequisites to use autologous DC that are prepared from the individual patient with autoimmune disease, to render such DC tolerogenic by exposure in vitro to factors that promote tolerogenicity, and to re-infuse these pretreated DC to the patient in order to treat the ongoing autoimmune disease and prevent its future exacerbation.