A strong signal in the E.G7–OVA tumour appeared in the CD8 channel (green, Fig. 4c,d and Supplementary Fig. 15 for n = 3 data) for mice immunized by the pErNP–OVA–CpG B vaccine, with the CD8 tumour-to-normal-tissue signal ratio (T/NT) reaching ~40 imaged on day 5 (48 h post injecting the probes, Fig. 4e). Here, CD8A is linked to neoplasm.