KIR2DL1 alleles differentially inhibit the cytotoxicity, degranulation, and cytokine production of YT-Indy cells. YT-Indy cells transfected with empty vector were used as control. (A) Specific lysis by YT-Indy cells expressing various alleles of KIR2DL1 (*00301, *00401, *006, and *010) were assessed against 721.221-Cw6 at various ratios of effector to target cells using a BADTA release assay. The E/T ratios were 40:1, 20:1, 10:1, and 5:1. Data shown are average of 3 independent experiments. (B) Specific lysis of target 721.221-Cw6 cells by YT-Indy transfectants was assessed at E/T = 20:1. Data shown are average of 9 independent experiments. ***P < .01. (C) Relative expression of CD107 at the surface of YT-Indy cells expressing various alleles of KIR2DL1 was detected by flow cytometry after challenge with target 721.221-Cw6 cells. The results represent the mean of 3 independent experiments; *P = .22, **P < .05. Error bars represent SD. (D) Production of IFN-γ in YT-Indy transfectants was assessed after stimulation with target 721.221-Cw6 cells. To separate effector from target cells, YT-Indy transfectants were first stained with CD45 antibody, followed by incubation with target cells. Cell mixtures were fixed, permeabilized, and stained with IFN-γ antibody. YT-Indy transfectants were gated based on CD45 (left panel), and IFN-γ production was assessed (right panels). Data shown are representative of 3 independent experiments.