Lacutamab specifically eliminates KIR3DL2-positive primary ATL cells in an autologous ADCC assay. CD4⁺ T cells from patients with KIR3DL2-positive ATL (n = 4) or patients with KIR3DL2-negative ATL (n = 4) were preincubated with alemtuzumab (triangles, positive control), isotype control (circles, negative control), or the anti-KIR3DL2 mAb lacutamab (red diamonds). After the addition of autologous NK cells at the indicated E/T ratio, the death of KIR3DL2⁺ (A) and KIR3DL2⁻ (B) CD4⁺ tumor cells, and NK cells (C) of patients with KIR3DL2⁺ ATL was monitored using 7-AAD cell viability stain. As control, the death of KIR3DL2⁻ tumor cells in patients with KIR3DL2⁻ ATL were also assessed (D). The results are expressed as the proportion of cell viability in each cellular population at a given E/T ratio. The cellular populations that were assessed are indicated above each plot. ***P < .001, ns, not significant (two-way ANOVA followed by Sidak’s post-test).