Fig. 2

Anti-CCR2 antibody abrogates the beneficial effect of PD-L1 blockade. This experiment included four groups of DM-hTAU mice treated either with: IgG, αPD-L1, αCCR2 + αPD-L1, or αCCR2. An additional group of WT mice served as healthy controls. (A) Schematic presentation of experimental design: αCCR2 was i.p. injected to DM-hTAU mice 3 days prior (Day − 3) to αPD-L1 or IgG (Day 0), and again on days 1, 5 and 9. The cognitive behavior of the animals was assessed 1 month after αPD-L1 treatment by T-maze, spontaneous alternation test in Y-maze, and novel object recognition. Subsequently, brains were removed, and aggregated human tau protein levels in the cortices was measured. (B) T-maze: Willingness to explore a novel environment is presented as percent of time spent by each mouse in a novel arm divided by the total time spent in all three arms (novel and two familiar arms. One-way ANOVA F_(4,56) = 9.068, ***p < 0.0001). (C) Spontaneous alternation in Y maze: The spontaneous alternation behavior of the mice is presented as percent alternation: number of alternations divided by number of possible triads (see Methods. One-way ANOVA F_(4,55) = 19.73, ***p < 0.0001). (D) Novel Object Recognition (NOR): novel object preference is presented as the percent time the mouse interacted with the novel object divided by the total time spent with both objects (One-way ANOVA F_(4,52) = 12.48, ***p < 0.0001). (B-D). Post-hoc uncorrected Fisher’s LSD multiple comparisons between DM-hTAU groups to WT: #p < 0.05, ##p < 0.01, ###p < 0.001. Post-hoc uncorrected Fisher’s LSD multiple comparisons between the DM-hTAU groups: *p < 0.05, **p < 0.01, ***p < 0.001. n = 9–18 mice per group. Results were combined from two independent experiments. Data are presented as mean ± s.e.m. (E) Cortical aggregated human tau protein levels were measured by HTRF immunoassay, and are presented as Delta F% normalized to the amount of total protein in each tissue (mg). One-way ANOVA F_(4,28) = 7.409, ***p = 0.0003. Post-hoc uncorrected Fisher’s LSD multiple comparisons between DM-hTAU groups to WT: ###p < 0.001. Post-hoc uncorrected Fisher’s LSD multiple comparisons between the DM-hTAU groups: *p < 0.05. n = 8–6 mice per group. Data are presented as mean ± s.e.m. (F) Pearson correlation coefficient test between the measured aggregated human tau protein and the T maze score of each mouse revealed a significant negative linear correlation. r_(Pearson) = − 0.5368, ***p < 0.001. (G) Representative images (scale bar - 100 μm) and (H) quantification of pyramidal neurons in the subiculum of female mice. One-way ANOVA F_(4,19) = 7.686, ***p = 0.0007. Post-hoc uncorrected Fisher’s LSD multiple comparisons between DM-hTAU groups to WT: ##p < 0.01, ###p < 0.001. Post-hoc uncorrected Fisher’s LSD multiple comparisons between the DM-hTAU groups: *p < 0.05, **p < 0.01. n = 3–6 mice per group. Data are presented as mean ± s.e.m. (I) Pearson correlation coefficient test between the neuronal survival in the female’s subiculum and the T maze score of each of them revealed a significant linear correlation. r_(Pearson) = 0.6697, ***p < 0.001