Defective lytic activity in CTLs and NK cells. (A) A CD8⁺ CTL clone derived from a healthy donor (▴) is compared with 2 different clones, derived from patient 6¹²  expressing perforin A91V and W374X (□ and ⋄) and 1 clone derived from patient 1¹²  lacking perforin expression (▵), for their cytolytic activity against P815 in the presence of anti-CD3 monoclonal antibody (mAb). (B-C) Polyclonal activated NK-cell populations derived from 2 healthy donors (▪ and ▴), from patient 6 (⋄), and patient 1 (▵) were tested in a cytolytic assay against the ⁵¹Cr-labeled FO-1 (B) and 721.221 (C) target cell lines. The percentages of target cell lysis at different effector-target (E/T) ratios are shown.