The concept of immune regulation mediated by specialized lymphocytes has risen to prominence in recent years. Few investigators now doubt the existence of lymphocytes that can suppress harmful immune responses. But, how many different subsets are there, how do they mediate their effects and what is their therapeutic potential? The articles in this special issue and Web Focus (see http://www.nature.com/nri/focus/reglymph) attempt to address these questions.
In a critical overview, Jean François Bach examines the experiments that gave rise to the concept of regulatory T cells. Kathryn Wood and Shimon Sakaguchi discuss the role of regulatory T cells, particularly the CD4+CD25+ subset, in transplantation settings. Much emphasis has been placed on the CD4+CD25+ regulatory T cells that are present in naive T-cell populations. But, some T-cell-mediated regulation is only apparent after exposure to antigen. These antigen-induced regulatory T cells are of great interest for the treatment of autoimmunity, and Matthias von Herrath and Leonard Harrison discuss their induction, functions and therapeutic potential.
