Panel A: Whole brain and photomicrographs for monocyte/macrophage marker F4/80 at 5 days after WBRT (4 Gy × 1, administered on day 20 of ISV + anti-CTLA-4 regimen) compared to untreated and single-treatment controls (dotted line = tumor area determined by serial H&E slides; brown = positive immunolabeling), and (panel B) quantified [***P < 0.001, *P < 0.05, mean ± SE with marker representing each individual mouse (i.e., average of 3 high-powered fields), ANOVA with post hoc Bonferroni, n ≥ 9, at least two independent animal experiments]. Panel C: qRT-PCR analysis for expression of immune-stimulatory Nos2 and -suppressive Arg1 in melanoma brain tumors at 5 days after WBRT + ISV + anti-CTLA-4, compared to single-treatment and untreated controls (**P < 0.01, *P < 0.05, shown as fold-change increase from untreated controls, mean ± SE, ANOVA with post hoc Bonferroni, n ≥ 8 in at least two independent animal experiments).