Fig. 9: Validation analysis of IDO1⁺ monocytes as new biomarkers for HLH.

a, b The proportions of IDO1⁺ monocytes in the validation biologically independent samples (n = 6 in HV, n = 4 in IM, n = 7 in HLH, n = 3 in HLH-T) by flow cytometry. The discrepancies between multiple groups were assessed using one-way ANOVA along with two-sided Tukey–Kramer post hoc testing (a). Two-sided Paired t-test was used for the three paired samples of HLH and HLH-T (b). c The proportions of IDO1⁺, HLA-DR⁺, CD163⁺, and CX3CR1⁺ monocytes in the IM (n = 4) and HLH (n = 5) biologically independent samples by flow cytometry. Two-sided Independent-samples t-test was applied. d In monocyte subsets of HLH patients (n = 5), comparative analysis of HLA-DR⁺/CD163⁺/CX3CR1⁺ proportions between IDO1⁺ and IDO1⁻ subpopulations (upper panel) and evaluation of IDO1⁺ proportions across positive/negative of HLA-DR, CD163, and CX3CR1 subgroups (lower panel). Two-sided Paired t-test was applied. e Box plot depicting the relative expression levels of L-Kynurenine across biologically independent sample groups (n = 6 in HV, n = 4 in IM, n = 5 in HLH). One-way ANOVA along with two-sided Tukey–Kramer post hoc testing was employed to assess the significance between multiple groups. f In THP1 and U937 cell lines, mRNA levels of inflammation-related cytokines were quantified via qRT-PCR following either IDO1 overexpression or exogenous KYN treatment for 48 h. g In primary CD3⁺ T cells and NK92 cell line, mRNA levels of inflammation-associated cytokines were quantified by qRT-PCR following exogenous KYN treatment for 48 h. The data were presented as means ± SEM (error bar) in (a–d).