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. 2021 Apr 16;12:678999. doi: 10.3389/fimmu.2021.678999

Figure 4.

Figure 4

Kynurenine mediates upregulation of inhibitory receptor on CD8+ T cells. (A) Frequency of PD1+CD8+ T cells in tumor ascites from WT C57BL/6 or IDOKO mice challenged i.p. with 1x10e7 IE9mp1-EV (n=5) or IE9mp1-mIDO1 (n=6) tumor cells on Day 48, as determined by flow cytometric analysis. (B, left) Kynurenine concentrations measured in IE9mp1-EV and IE9mp1-mIDO1 tumor cell culture supernatant by colorimetric assay. (B, right) Frequency of PD1+CD8+ T cells, from WT C57BL/6 mice spleens, co-cultured with 1µg/mL anti-CD3/CD28 in IE9mp1-mIDO1 or IE9mp1-EV tumor cell culture supernatant for 48 hr. PD1+CD8+ T cell frequency was determined by flow cytometric analysis. (C) PD-1, (D) KLRG1, and (E) TIM3 expression analyzed by flow cytometric analysis on T lymphocytes from WT C57BL/6 mice activated with 1µg/mL anti-CD3/CD28 and with treated kynurenine. *p < 0.05, **p < 0.01, ****p < 0.0001, by Student’s t test (A–E). The data represent means ± SEM of three independent experiments performed in triplicate.