Heroes or villains? T regulatory cells in malaria infection.

Infection with Plasmodium parasites can cause severe disease due to a lack of protective immune responses to clear parasitemia, or to the host's inability to control excessive inflammation resulting in immunopathology. T regulatory cells (Tregs), key mediators of immune homeostasis, are increased in number and modulate disease in human and murine malaria. Several recent studies provide new insights into the mechanisms and functional consequences of Treg induction by P. falciparum. This review integrates and discusses the findings published on Tregs in human and murine malaria to date, with emphasis on Treg induction (host components, kinetics and parasite-dependence) and their diverse roles (protective or pathological) during infection. Copyright 2009 Elsevier Ltd. All rights reserved.