2.7. Enzyme-Linked Immunosorbent Assay (ELISA) Target cells (K562, H929, MM.1R, U266, RPMI8226) were plated into a 96-well U-bottom plate at a density of 2 × 104 cells/well and co-cultured with effector cells (Coc NK92, CAR NK92) at a ratio of 1:1 for 4 h at 37 °C. ...