ABSTRACT
In Chapter 7 we saw how T cells develop in the thymus to give a diverse and highly selected population of mature naive T cells. These long-lived cells circulate between the blood and the lymph, passing through secondary lymphoid tissues where they can meet and be activated by antigens. Dendritic cells transport pathogens and their antigens from sites of infection to the T-cell areas of the draining lymph node. When a T-cell receptor recognizes the complex of a peptide antigen and an MHC molecule on a dendritic cell, it activates the T cell, which then undergoes proliferation and differentiation to become a clone of effector T cells. Effector T cells are diverse in function and phenotype. Some remain in the secondary lymphoid tissue to help B cells become antibody-producing cells; others travel to sites of infection where they work in various ways to terminate infection.
