This monograph, for the first time, presents a comprehensive overview of different mechanisms of immune dysfunction in cancer as well as therapeutic approaches to their correction. It discusses a number of new mechanisms that have never been discussed in a monograph before: T-cell inhibitory molecules, regulatory tolerogenic DCs, and signaling pathways in antigen-presenting cells involved in T-cell tolerance. There is now a pressing need to discuss the already described and newly emerging mechanisms to see how they can be put together in a more or less cohesive structure and how they can help to improve immune response to tumors.