REAGENT or RESOURCE	SOURCE	IDENTIFIER
Antibodies
p4E-BP1	Cell Signaling	RRID:AB_560835
4E-BP1	Cell Signaling	RRID:AB_2097841
p70S6K	Cell Signaling	RRID:AB_2265913
IDO1	Sigma	RRID:AB_1846221
IDO2	Sant Cruz	RRID:AB_374159
beta-Actin	Cell Signaling	RRID:AB_2242334
IDO1	eBioscience	RRID:AB_831071
CD4	eBioscience	RRID:AB_10718983
CD8	Biolegend	RRID:AB_962672
B220/CD45R	BD Bioscience	RRID:AB_394619
CD11c	Biolegend	RRID:AB_959596
CD11b	BD Bioscience	RRID:AB_1727421
PDCA-1	eBioscience	RRID:AB_763417
CD45.2	Biolegend	RRID:AB_492872
Foxp3	eBioscience	RRID:AB_465936
p4EBP1	Cell Signaling	RRID:AB_2097838
pS6	Cell Signaling	RRID:AB_2797646
pAKT	eBioscience	RRID:AB_2574125
IFNγ	Biolegend	RRID:AB_893526
CD28	BD Bioscience	RRID: AB_2737780
CD3e	BD Bioscience	RRID:AB_394728
mTOR	Invitrogen	RRID:AB_11155001
IgDb	BD Bioscience	RRID:AB_394894
AF594-donkey anti-rabbit IgG secondary	ThermoFisher	RRID:AB_141359
HRP-anti-rabbit IgG secondary	Cell Signaling	RRID:AB_2099233
HRP-anti-mouse IgG secondary	Cell Signaling	RRID:AB_330924
hFAB™ Rhodamine Anti-GAPDH	Bio-Rad	Cat# 12004168
Chemicals, peptides, and recombinant proteins
L-Tryptophan	Sigma	T0254
L-Kynurenine	Sigma	K8625
Indole-3-acetate	Sigma	I5148-2G
5-Thio-D-Glucose	Sigma	88635
Tryptamine	Sigma	193747
Signal Fire Luminol Reagent	Cell Signaling	6883
HyGLO™ Chemiluminescent HRP Detection Reagent	Denville Scientific	E2500
PVDF Stripping Buffer	ThermoFisher	46430
dsDNA	Sigma	D8515
p-nitrophenol phosphate (PNPP) substrate	ThermoFisher	34045
McCoy's 5A media	ThermoFisher	16600082
Tryptophan synthetic chows	Research Diets	A11022501-03
CD4 microbeads (mouse)	Miltenyi Biotech	130-104-454
CD11c microbeads (mouse)	Miltenyi Biotech	130-125-835
Rneasy mini kit	Qiagen	74104
Critical commercial assays
Xbridge Amide 3.5 μm × 2.1 mm x 100 mm chromatography column	Waters	186004860
Mouse KMO ELISA kit	Aviva Systems Biology	OKEH05543
Experimental models: Organisms/strains
Specific Pathogen Free Adult C57BL/6J	UF Rodent Colony	N/A
Specific Pathogen Free Adult B6.Sle1.Sle2.Sle3	UF Rodent Colony	N/A
Germ Free Adult C57BL/6J	UC Rodent Colony	N/A
Germ Free Adult B6.Sle1.Sle2.Sle3	UC Rodent Colony	N/A
Oligonucleotides
Ido1 (F: CCCACACTGAGCACGGACGG; R: TTGCGGGGCAGCACCTTTCG)	Metz et al. (2014)	N/A
Tdo2 (F: CATGGCTGGAAAGAACAC; R: GGAGTGCACGGTATGAC)	Pilotte et al. (2012).	N/A
Ppia (F: GCTGTTTGCAGACAAAGTTCCA; R: CGTGTAAAGTCACCACCCTGG)	This Paper	N/A
Kmo (F: ATGGCATCGTCTGATACTCAGG; R: CCCTAGCTTCGTACACATCAACT)	Wang et al. (2018)	N/A
Kat2 (F: ATGAATTACTCACGGTTCCTCAC; R: AACATGCTCGGGTTTGGAGAT)	Wang et al. (2018)	N/A
3Hao (F: GAACGCCGTGTGAGAGTGAA; R: CCAACGAACATGATTTTGAGCTG)	Wang et al. (2018)	N/A
Software and algorithms
FlowJo V10	Tree Star	https://www.flowjo.com/solutions/flowjo/downloads
Prism 9.0	Graphpad	https://www.graphpad.com/scientific-software/prism/
ImageJ	NIH	https://imagej.nih.gov/ij/