In this study, we showed that TI-NK cells act as major contributors to early CCL5/IFN-ɣ production along anti-HER2 antibody treatment in primary breast cancer patients, disclosing the role of the IFN-ɣ/CCL5/CXCL9 axis in the effectiveness of neoadjuvant treatment with anti-HER2 antibodies. Here, CXCL9 is linked to breast cancer.