It has long been appreciated that certain subsets of T cells are capable of suppressing immune reactions. Initially, such T cells were described as CD8+ suppressor T cells (Ts) and there is a vast body of research spanning 30 years that describes the immunobiology of CD8+ Ts. However, studies on CD8+ Ts have suffered from the inability to distinguish CD8+ Ts from CD8+ T cells of other phenotypes. Here we present a brief history of CD8+ Ts, a review of recent progress distinguishing CD8+ Ts as a unique subset of CD8+ T cells, and an overview of the evolving immunological context in which CD8+ Ts function.
