CD8A and breast cancer: As expected (Shrikant & Mescher, 1999; Shrikant et al, 1999), adoptively transferred naive (CD44loCD62Lhi) Ptpn2fl/fl OT‐1 CD8+ T cells had no overt effect on the growth of AT‐3‐OVA mammary tumours when compared to vehicle‐treated tumour‐bearing mice (Fig 2A).