Molecular signals and genetic reprogramming in peripheral T-cell differentiation

Rearrangement of gene segments occurs in T lymphocytes during thymic develo pment as the T-cell receptor (TCR) is first expressed, allowing T cells to become central regulators of antigen specificity in the acquired immune sys tem. However, further development of T cells occurs after population of per ipheral lymphoid tissues, which can result in T-cell expansion and differen tiation into effectors of various immune function, or progression to memory T cells, anergic cells or death by apoptosis. This review focuses on more recent developments concerning the choices that peripheral T cells make bet ween first encountering antigen through TCR recognition and death. These de cisions are associated with a process of genetic reprogramming that alters the behaviour of cells so that immune responses are appropriately regulated .