Depletion and overexpression of cxcr3.3 result in opposite M. marinum infection outcomes. Cxcr3.3‐deficient larvae had a higher bacterial burden than their WT siblings at 4 days following blood island (BI) infection with 300 CFU of M. marinum (Mm) (A and B). We transiently overexpressed cxcr3.3 in AB/TL embryos by injection of a CMV: cxcr3.3 construct at 0 hpf and observed that bacterial burden was lower in larvae overexpressing the gene than in noninjected controls at 4 dpi (C and D). To rescue the cxcr3.3–/– phenotype, we restored the expression of the gene by transiently overexpressing it (CMV: cxcr3.3) in one‐half of the cxcr3.3 mutants (cxcr3.3–/– rescued). The bacterial burden was lower in the rescued group than in noninjected cxcr3.3 mutants (cxcr3.3–/–) and similar to the bacterial burden in WT controls (E and F). Results from qPCR show that cxcr3.2 expression remained unaltered in the cxcr3.3 mutants and that it was induced upon infection (G), whereas cxcr3.3 expression was lower in cxcr3.2–/– and was moderately induced upon Mm infection (H). The ligand cxcl11aa was induced upon infection independently of any of the cxcr3 genes. In all cases, systemic infection was done at 28 hpf in the BI with 300 CFU of Mm. The bacterial burden data were analyzed using a two‐tailed t‐test (A–C) and a one‐way ANOVA (E). Results are shown as mean ± sem (ns P > 0.05, *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001) and combine data of 3 independent replicates of 20–30 larvae each. The qPCR data were analyzed with the 2–∆∆Ct method and a one‐way ANOVA. Results are plotted as mean ± sem (ns P > 0.05, *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001)
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