Right Time, Right Place

Regulatory T cells are highly immunosuppressive lymphocytes that help the body avoid autoimmunity and overzealous immune reactions. However, their existence also presents a dilemma for the immune system, because they might inadvertently shut down useful pathogen-specific immune responses. Lund et al . (see the Perspective by Kassiotis and O9Garra) present evidence that suggests that regulatory T cells can in fact optimize immune responses during the early stages of infection. Using a mouse model of herpes simplex virus infection, depleting regulatory T cells delayed the arrival of the relevant immune cells at the site of infection. At the same time, inflammatory chemokines became elevated in the lymph nodes. Thus, under normal circumstances, regulatory T cells may minimize the expression of these soluble factors in the lymph nodes so as to redirect immune cells for a timely arrival at the site of infection. J. M. Lund, L. Hsing, T. T. Pham, A. Y. Rudensky, Coordination of early protective immunity to viral infection by regulatory T cells. Science 320 , 1220-1224 (2008). [Abstract][Full Text] G. Kassiotis, A. O9Garra, Immunity benefits from a little suppression . Science 320 , 1168-1169 (2008). [Summary][Full Text]