Fig. 4

Activation of KYN pathway in monocytic cell lines upon macrophage differentiation and IFNγ stimulation. A Correlation analysis of KYN/TRP ratio with serum CRP concentrations. B Comparison of median values of the percentage of major white blood cell types in patients with DILD and recovered patients. C Expression levels of IDO1 mRNA were examined using RT-qPCR in undifferentiated (U937 and THP1) cells and differentiated (dU937 and dTHP1) macrophage-like cell lines. D Fold changes of IDO1 mRNA expression levels upon vehicle (10% FBS-PBS) or IFNγ (10 ng/mL) treatment were examined in differentiated macrophage cell lines (dTHP1 and dU937). E Western blotting analysis of IDO1 expression in dU937 and dTHP1 cells upon treatment with vehicle (10% FBS-PBS) or IFNγ (10 ng/mL) for 24 h. GAPDH expression was analyzed as a loading control. Uncropped images are shown in Additional file 4. F Levels of TRP, KYN, and QUNA were measured in undifferentiated or differentiated THP1 cell supernatant treated with 0.1% (v/v) DMSO or PMA at 10 ng/mL for 24, 48, 72, and 96 h. The metabolite level in undifferentiated THP1 cells after 24 h DMSO exposure was set as 1. The time-dependent changes of each metabolite level in undifferentiated cells and levels between undifferentiated and differentiated THP1 cells were statistically compared. G and H Relative levels of TRP, KYN, and QUNA in supernatant and whole cell lysate of dTHP1 cells treated with 10% FBS-PBS (control) or IFNγ (10 ng/mL) for 24 h are shown. Each bar represents the mean ± standard deviation of three independent experiments. Statistical significance of mean or median values was tested using Student’s t-test or Mann–Whitney U test (ns, not significant; *p-value < 0.05, **p-value < 0.01; ***p-value < 0.001), respectively. Bonferroni correction was conducted for multiple comparisons