Demonstration of IDO1 expression and kynurenine production in response to M. tuberculosis infection and regulation of M. tuberculosis-specific T-cell responses by kynurenines.

(A) Immunohistochemistry staining of formalin-fixed, paraffin-embedded tissue of a murine pulmonary TB lesion stained with anti-IDO polyclonal antibody; staining representative of lesions from five animals. Bar is equal to 200 nm. Human monocyte-derived dendritic cells (DCs) (B) and macrophages (C) were infected with M. tuberculosis H37Rv or stimulated with irradiated and heat-killed M. tuberculosis H37Rv for 24 h and indoleamine 2,3 dioxygenase 1 (IDO1) gene expression was measured by qPCR. Mean and standard deviation (SD) of fold-change IDO1 gene expression of one donor representative of four. Line indicates minimal significant fold change threshold equal to 1.5. DCs (D) and macrophages (E) were infected with M. tuberculosis H37Rv and cell culture supernatants were collected at indicated times for measurement of kynurenines by HPLC; kynurenine levels from uninfected controls were subtracted. Means and SD of four donors are depicted (C and D). Star indicates significance (pF) Human monocyte-derived DCs were pulsed with purified protein derivative (PPD) and mannosylated lipoarabinomannan (ManLAM) and co-cultured for 4 days with autologous CFSE-labeled purified T cells (DC:T cell ratio 1∶20) in the presence or absence of 1-methyl-DL-tryptophan (1-MT-DL) and 3-OH-kynurenine (Kyn). Cell proliferation was assessed by CFSE dilution using flowcytometry. Figure representative of three independent experiments (ANOVA F = 4.1 for CD+CD4+ cells and F = 3.3 for CD3+CD8+ cells, p