CD8A and neoplasm: The repression of tumour growth was accompanied by the significant infiltration of mCherry+ CD8+ HER‐2 CAR T cells into tumours (Fig 8D); infiltrating HER‐2 T cells exhibited increased cytotoxic capacity (as assessed by IFNγ and TNF expression after PMA/ionomycin treatment ex vivo) (Fig EV5F).