IDO1 and infection: There are important clinical implications for this work since activity along the kynurenine pathway is strongly induced and enhanced by immune system activity and the presence of pro-inflammatory cytokines, raising the strong possibility that stress (via glucocorticoids and tryptophan-2,3-dioxygenase, TDO) or infection (via indolamine-2,3-dioxygenase, IDO) could have not only acute and transient effects on cerebral function but, if experienced during gestation could significantly interfere with brain development.