To this end, naive OT‐1;Ptpn2fl/fl or OT‐1;Lck‐Cre;Ptpn2fl/fl CD8+ T cells were adoptively transferred into immunocompetent and non‐irradiated congenic C57BL/6 hosts bearing syngeneic tumours arising from AT‐3‐OVA cells inoculated into the mammary fat pad (Fig 2A). The gene discussed is LCK; the disease is neoplasm.