Responses to weak affinity tumour antigens are also enhanced by knockout of PTPN22 [160] whilst PTPN2 deficient T-cells were more efficient in restraining tumours in an AT3-OVA mammary carcinoma model, expressing lower frequencies of PD-1 or LAG-3 indicating that they may be less susceptible to exhaustion [161]. Here, PDCD1 is linked to breast carcinoma.