FIG. 2.

HTLV-1-infected primary CD4⁺ T cells are resistant to lysis by autologous natural killer cells. HTLV-1-infected CD4⁺ T cells, mock-infected CD4⁺ T cells, and K562 cells were used as target cells in a 4-h cytotoxic assay with “resting”(A and B) or IL-2-treated (C) (1,000 U of IL-2/ml overnight) autologous NK cells as effector cells. E:T ratios of 5:1, 10:1, and 20:1 were used. All groups were performed in triplicates. Each experiment involved CD4⁺ T cells and NK cells from two different donors. Statistical analysis was performed by using single-tail analysis of variance and Student t tests (*, P < 0.05).