Fig. 6
Exogenous S100A9 enhances PD-L1 expression in monocytes to inhibit T-cell proliferation and cytotoxicity. a Representative flow cytometric plot (left) and quantification (right) of PD-L1 levels in primary human CD14+ monocytes (n = 3) treated with PBS or rS100A9 for 8 h. b Similar to (a), PD-L1 levels in THP-1 cells treated with PBS (n = 3), rS100A9 (n = 3), or pre-incubated tasquinimod plus rS100A9 (n = 3) for 24 h.c Schematic representation of the co-culture system. d Representative CFSE dilution profiles of T cells (left) and the percentage of highly proliferated CFSElow T cells at 96 h (right, n = 3). The peak of the CFSE-labelled unstimulated cells (gray, filled) is also shown. e The percentage of highly proliferated CFSElow T cells at 96 h in four groups: pre-incubated with IgG, pre-incubated with IgG and co-cultured with S100A9-treated THP-1, pre-incubated with αPD-1 antibody, pre-incubated with αPD-1 antibody and co-cultured with S100A9-treated THP-1. (n = 3). f The RUNX3 and TBX21 mRNA levels in T cells co-cultured with THP-1 cells treated with PBS or rS100A9 for 24 h. g Schematic showing S100A9 binding sites on CD274 promoter (left). Luciferase activities relative to the control were shown on the right (n = 3). MFI, mean of fluorescence intensity. CFSE: carboxyfluorescein succinimidyl ester. Unsti: unstimulated. Data are represented as mean ± S.E.M. P value in (a) was determined by two-tailed paired sample t-test.P value in (d) was determined using two-tailed unpaired Student’s t-tests. P value in (b) was determined by one-way ANOVA. P values in (e-g) were evaluated using 2-way ANOVA. *P < 0.05, **P < 0·01, ***P < 0.001 and ****P < 0.0001