IDO1 and asthma: This study revealed that PCF can downregulate ERK and Toll-2 and upregulate IDO and Toll-9 expression, reduce IL-4 level, and increase IL-12, IFN-α, and IFN-r in BALF, thus restoring the balance of T cells via TLRs and DCs to improve airway inflammation and reduce asthma symptoms.