Besides varying direct effects of trastuzumab on the different tumor cells, one possible additional explanation for the weak lysis of PDAC cell lines by PBL from cancer patients is our observation of a significantly decreased CD16 expression on Vδ2-positive γδ T cells within the PBL of PDAC patients (Figure 2A, right panel), in contrast to TCR γδ-negative NK cells (Figure 2A, left panel), which was not present in age-matched HDs or patients with other different (cancer) diseases (shortly before surgery, listed in Section “Materials and Methods”) (Figure 2A). Here, FCGR3A is linked to neoplasm.