CD44DL is mediated by NK cells. LD-PBL were activated for 3 days with 100 U/mL rIL-2 and tested for the ability to lyse TNP-MC1 target cells in the presence of no antibody (○), anti-CD44(Fab) × anti-DNP(Fab) bsAb (•), anti-CD3(Fab) × anti-DNP(Fab) bsAb (▴), and anti-DNP Ab (□). Effector cells were as follows: upper panel, total LD-PBL; middle panel, electronically sorted CD16⁻ LD-PBL; lower panel, sorted CD16⁺ LD-PBL.