Impact of mAb 4D7 on MM-derived primary human NK cell activity. (A) Schematic of the experimental design. Primary NK cells were cocultured with target cell lines for 4 hours in the presence of 4D7 mAb or isotype control (murine IgG1, 10 μg/mL). (B) Normalized CD107a degranulation results for autologous (top), U266 (middle), and RPMI8226 (bottom) target cells. (C) Normalized IFN-γ production results for autologous (top), U266 (middle), and RPMI8226 (bottom) target cells. NK cells were cocultured with target cells (E:T ratio 1:3), and subsequently stained for CD107a, CD16, CD56, NKG2A, and NKG2C (2 μg/mL each). Supernatants were collected for IFN-γ measurements. Data were acquired using a CytoFLEX flow cytometer and analyzed with GraphPad Prism v10. CD107a-positive NK cell percentages were calculated and normalized as described in Figure 4. Results represent the average of 6 patients with MM, with experiments performed in triplicate for each donor. Error bars represent ± SD. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001 (2-way ANOVA). ns, not significant.