Therefore, to examine whether the blockade of mPD1/mPD–L1 interaction by rabbit IgG against JT–mPD1 as shown in vitro can also be translated to anti-tumor activity in vivo, passive immunization/administration of the rabbit IgG in a syngeneic mouse model, involving BALB/c mice engrafted with BALB/c-derived mammary carcinoma (D2F2/E2) cells expressing human Her-2, was carried out. The gene discussed is ERBB2; the disease is breast carcinoma.