This book describes the activation and functions of effector T cells. We'll begin by discussing the different types of T cells, which are CD4+ and CD8+ T cells. Then, we'll move on to the specific functions of the different types and subtypes of T cells. We'll explore how different infections can induce T cell responses in different ways, and how this in turn affects the overall T cell-based immune response. This book is designed to be a convenient and concise resource regarding T cell activation and function.
This book is ideal for undergraduate students majoring in biology or health sciences, as well as graduate and medical students interested in immunology.
T cells are a type of immune lymphocyte that originate in the thymus and are involved primarily in adaptive or acquired immunity, however various subtypes play a role in innate immunity.
T cells are an important part of the immune system. They provide immunity against a variety of different pathogens, including both extracellular and intracellular pathogens. T cells utilize many mechanisms to fight infections. CD4+ helper T cells produce cytokines to activate effector immune cells, such as CD8+ T cells, macrophages, B cells, and neutrophils. CD8+ T cells can directly kill infected cells. Although there are innate immune cells that can provide many of these functions, T cells provide the benefit of memory. When antigen is initially encountered, naïve T cells that recognize that antigen are activated and proliferate. After the infection is cleared, most of the activated T cells die, but a few remain and become memory cells. Upon re-infection, memory T cells quickly respond and are able to fight off the secondary infection more rapidly. Acquired immunity is an important part of protection against serious infections.
T cells have a variety of different roles during infection. When a T cell is activated by antigen, a complex signaling cascade begins, which results in development of effector functions (Smith-Garvin, Koretzky, and Jordan 2009, 591-619). The cytokines present during activation and the presence of either a CD4 or CD8 co-receptor, influence the effector function a T cell will possess after activation.