T cells are a type of white blood cells that play an important role in the adaptive immune response. T cell receptors are present on the surface of T cells which distinguish them from the other cells. The T cells are formed in the bone marrow from the hematopoietic stem cells. These are the stem cells that give rise to different types of blood cells. T cells do not mature in the bone marrow. The developing cells migrate to thymus where they mature into several different types of T cells. The differentiated subtypes of T cells have a major role in controlling and shaping the immune response. This book is compiled in such a manner, that it will provide in-depth knowledge about the T cells. It includes some of the vital pieces of work being conducted across the world, on various topics related to T cells. This book serves as a valuable source of reference for graduate and post graduate students.