Long-term competitive assay clarifies strong survival advantage in CD48 knockout ATLL cells. Long-term competitive assay by using primary NK cells isolated from healthy donor #1, healthy donor #4, chronic-type ATLL patient #5, and acute-type ATLL patient #6. Cells were mixed every 2 days at an E:T ratio of 1:2. The ratios of the GFP⁺ and Lyt2⁺ populations were normalized to the value at day 0. Growth curves represent the mean of 3 replicates. Error bars represent the SEM of replicates. ∗∗P < .01, and ∗∗∗P < .001, Welch 2-sample t test.