Indoleamine 2,3-dioxygenase in infection: the paradox of an evasive strategy that benefits the host

Initially recognized in infection because of antimicrobial activity (‘tryptophan starvation’), indoleamine 2,3-dioxygenase (IDO) is widely involved in host immune homeostasis and even immune evasion by microbes that establish commensalism or chronic infection. This review deals with recent findings that could gain IDO a reputation of Jack-of-all-trades in mammalian host/microbe interactions.