Fig. 4
Effects of CD95 (Fas)-ligation on serial killing by non-irradiated and irradiated NK-92 cells. Non-irradiated or 10 Gy irradiated cells were cultured for 1 day with nothing, 1 ug/ml control IgM or IgM anti-Fas. Because K562 cells lack Fas, they were used as tumor ‘target’ cells to prevent addition of anti-Fas-initiated “suicide” to target cell killing by NK-92 cells. Cytotoxic activity towards K562 cells was measured after 8 h. E:T ratios are approximate. A Anti-Fas ligation limited to non-irradiated NK-92 cells. Insert: LU50/1 M non-irradiated NK-92 cell, by treatment. B Anti-Fas ligation of 10 Gy irradiated NK-92 cells. Insert: LU50/1 M irradiated NK-92 cell, by treatment. [***p-value < 0.001 via regression analysis]. KFs A, B The KFs calculated for a 1:1 E:T for A, the non-irradiated control alone, with IgM or with anti-Fas were 0.36, 0.34, and 0.22, respectively. For B, the KFs for the irradiated cells alone, with IgM or with anti-Fas were 0.30, 0.30 and 0.03 respectively. The loss of KF for the irradiated and anti-Fas combination exceeded both additive and synergistic effects estimated based on the losses from single treatments