Figure 1.

The stage of differentiation in pancreatic tumors correlated with susceptibility to NK cell-mediated cytotoxicity. The surface receptor expression of CD44, CD54, and MHC-class I on pancreatic tumors were assessed by flow cytometry after staining with PE-conjugated antibodies. Isotype control antibodies were used to determine non-specific binding. Numbers in each histogram represent percent/mean channel fluorescence (MFI). (A) Freshly isolated NK cells were left untreated or treated with anti-CD16 mAb (3 μg/mL), IL-2 (1000 U/mL), or the combination of anti-CD16 mAb (3 μg/mL) and IL-2 (1000 U/mL) for 18 h before they were added to the cultures of ⁵¹Cr labeled MP2, Panc-1, BXPC3, HPAF, Capan, or PL12. NK cell-mediated cytotoxicity was determined using 4 h ⁵¹Cr release assay, and the lytic units 30/10⁶ cells were determined using inverse numbers of NK cells required to lyse 30% of the target cells × 100. (B) One of several representative experiments is shown in the figure (please also see Supplementary Figure S1A).