Metabolic alterations within TRP/KYN pathway during P yoelii infection. Plasma was obtained from female and male control and infected mice at multiple time points. Normalized relative intensity measurements of metabolites were obtained from LC-MS/MS. (A) TRP (B) KYN (C) KTR as a measurement of Ido1 activity. (D) Serotonin levels measured in an ELISA and (E) normalized relative intensity of serotonin metabolite, 5-HIAA (∗P < .05, ∗∗P < .01, ∗∗∗P < .001).