Figure 7

TLR2, but not the microbiome, determines macrophage load of Mma20 from the gut in zebrafish larvae. (A) Schematic of the experimental design. (B) Representative fluorescence images showing macrophages containing Mma20 bacteria in different body regions (representative images are tlr2 wild-type larvae under germ-free (GF) condition). Bacteria are shown in magenta. Macrophages are shown in cyan. Scale bar: 100 µm for full-body images; 25 µm for zooms. The bottom graphs illustrate the spatial colocalization patterns of macrophages and bacteria. (C-E) Quantification of the number of bacteria-containing macrophages in the full body (C), anterior region (D), and posterior region (E). Wild-type larvae had significantly more infected macrophages than tlr2 mutants under both GF and CONVD conditions in the full body and anterior regions, with no significant differences between GF and CONVD conditions. For the posterior body region, no significance was found among groups. Macrophages containing bacteria were manually counted across the full z-stack for each region. Each z-slice was examined to verify that individual bacteria-containing macrophages were counted once and only once. The data from GF tlr2^+/+ (n=25) group, GF tlr2^-/- (n=21) group, CONVD tlr2^+/+ (n=24) group and CONVD tlr2^-/- (n=30) group are based on two independent experiments. Statistical significant difference was determined by one-way ANOVA, red arrows point to the median, ns, non-significant, *, P < 0.05, **, P < 0.01, ****, P < 0.0001.