[Physiology and physiopathology of the immune system: initiation and termination of immune responses].

The immune system is regulated in a complex fashion that allows flexibility in the response to pathogens and enables close control at multiple points, to prevent an undesired response. Indeed, for effective action, it is not only essential that the immune system possesses good effectors, but that the performance of the effectors be properly monitored back to avoid autoimmune reactions or excessive inflammatory response that might imperil the fitness of the organism. Herein, we show the importance of the dendritic cell population in the initiation of an effective immune response and we describe an experimental approach to optimize the dendritic cell-based immunotherapy in cancer murine models. We also characterize a T cell activation-limiting mechanism that is likely to play a physiological role in the down-regulation of the immune responses.