Fig. 6: The genetic ablation of PDL1 in macrophages reduces the tumor burden in a MYC-driven model of B-cell lymphoma.

C57BL/6 mice were intravenously injected with 1 Mio >90% pure lymphoma cells isolated from the spleens of Eμ-Myc-transgenic donors; the frequencies of PDL1⁺ macrophages among all F4/80⁺ macrophages in spleen (A) and pooled axillary and inguinal lymph node (B) preparations were determined by flow cytometry at the study endpoint (10 days post injection), relative to non-tumor bearing control tissues. Representative histograms are shown alongside summary plots of one study in (B) and two pooled studies in (A). Each symbol represents one mouse. C–L Mrc1^Cre-ERTCd274^fl/fl mice and their Cd274^fl/fl littermates were treated intraperitoneally with tamoxifen for one week prior to the intravenous transplantation of 1 Mio MYC-expressing lymphoma cells; tamoxifen administration was continued twice weekly until the study endpoint (10 days post injection). The efficiency of PDL1 ablation is shown in C and D for splenic and lymph node macrophages, respectively; representative histograms are shown alongside summary plots of two pooled studies. Spleen and lymph node weights at the study endpoint are shown in (E, F). The splenic and lymph node tumor burden, i.e. the frequency of tumor cells among all live leukocytes, is shown in (G, H). Splenic and lymph node CD8⁺ T-cell proliferation, i.e. the frequency of Ki67⁺ among all CD8⁺ T-cells is shown in (I, J). MHCI and MHCII expression by macrophages is shown in (K, L). Representative contour plots or histograms are shown alongside summary plots of two pooled studies in (G–L). p-values were calculated by unpaired two-tailed Mann-Whitney test throughout. **p < 0.01; ***p < 0.005; ****p < 0.001; n.s. not significant.