Fig. 6: Blocking the lytC_22–Slamf4 interaction can reverse the effect of lytC_22 and P. anaerobius on MDSC modulation.
a, Schematic of the lytC_22–Slamf4 binding sites and their corresponding prediction result (pink, lytC_22; cyan, Slamf4 and yellow dash, hydrogen bond). LytC_22 binds to Slamf4 protein with a binding energy of −416.43 kcal mol−1. LytC_22 is attached to Slamf4 with seven key residues: Glu570, Asp653, Asp725, Tyr661, Asp712, Arg660 and Lys669. b, LytC_22 mutant protein was purified following substitution of key binding residues with alanine. GST-tag pulldown of the GST–lytC_22 mutant with recombinant hSLAMF4. c, MDSCs were treated with lytC_22 or its mutant. Flow cytometry was used to determine the MFI of Arg1 and iNOS in MDSCs; n = 3 biologically independent samples. d, Following MDSC pre-treatment with lytC_22 or lytC_22 mutant protein, the expression of IFN-γ and GzmB in CD4+ and CD8+ T cells was assessed after co-culture with MDSCs; n = 4 biologically independent samples. e–g, Anti-Slamf4 reversed lytC_22-induced anti-PD1 resistance in the MC38 allograft mouse model; n = 6 mice per group. e, Tumour growth (left) and tumour weight (left). f, Percentage of MDSCs (left) as well as Arg1+ (middle) and iNOS+(right) MDSCs in tumours from mice in the different treatment groups. g, Percentage of IFN-γ+CD8+ T cells in the tumours. c–g, Data are the mean ± s.e.m. P values were calculated using a one-way ANOVA, followed by Tukey’s post-hoc test (c,d) or a one-way ANOVA, followed by Fisher’s least significant difference test (e–g).
