This volume reviews the current state of research on immune checkpoints and offers novel concepts. It discusses the two most important immune checkpoints: T lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death-1 (PD-1). It shows that antagonistic antibodies against these two molecules are highly effective in the treatment of various cancers and that PD-1 and CTLA-4 have been linked to the suppression of T-cell receptor signaling and co-stimulatory molecules. Further, the volume examines other agents, a number of cells, receptors and signaling molecules, that are also involved in the regulation of T-cell activation and extends the concept of immune checkpoints to "molecules and cells that negatively regulate T-cell activation". Playing essential roles in immune homeostasis, they could offer new targets for cancer immunotherapy, and for the therapy of autoimmune diseases. Written by internationally respected scientists, this book will appeal to basic scientists, clinicians, drug development researchers, and advanced students alike.