Holding T cells in check--a new role for complement regulators?

Complement is not only part of the innate immune system, but has also been implicated in adaptive immunity. The role of complement and its regulatory proteins in modulating T cell activity has been the focus of several recent studies. These, which have included work on the membrane co-factor protein (MCP or CD46), decay accelerating factor (DAF or CD55) and CD59, indicate that complement regulators can influence the proliferative capacity of T cells and their ability to produce cytokines, influencing the outcome of a T cell response to a given antigen. Here we review these studies, which reveal another important link between the innate and the adaptive immune system.