Fig. 3

Significant disparity in anti-human epidermal growth factor receptor 2 (anti-HER2) interferon (IFN)-γ⁺ T cell immune responses between patients with pathologic complete response (pCR) and patients with non-pCR. a Significantly elevated anti-HER2 CD4⁺ T cell responses by IFN-γ enzyme-linked immunosorbent spot analysis (ELISPOT) are observed in patients with HER2^pos invasive breast cancer achieving pCR (n = 16) following neoadjuvant trastuzumab and chemotherapy (T + C), compared with patients with non-pCR (n = 24). Peripheral blood mononuclear cells (PBMC) from patients with pCR and non-pCR were stimulated ex vivo with six HER2-derived class II peptides and IFN-γ production via ELISPOT was compared. Responses are stratified by anti-HER2 responsivity, repertoire, and cumulative response. b Evaluable HLA-A2.1^pos PBMC from patients with pCR (n = 6; black bars) and non-pCR (n = 4; white bars) were stimulated ex vivo with two HER2-derived class I peptides, HER2 _369–377 and HER2 _689–697, and IFN-γ production via ELISPOT was compared. Phorbol-12-myristate 13-acetate (PMA) and ionomycin served as positive control. Results are expressed as mean spot-forming cells (SFC)/2 × 10⁵ cells ± standard error of the mean