Stimulation of primary human T cells with gamma cytokines IL-15 or IL-2 generates cells with a bystander phenotype. (A) Representative flow plots demonstrating the gating strategy used to identify T cells expressing the bystander markers CD8, CD160, NKG2D, and CCL5 in unstimulated cells and cells stimulated with IL-2. Cells were gated on CD3⁺/CD8⁺ double-positive T cells and subsequently gated on bystander markers CCL5, NKG2D, and CD160. CD8/CCL5 double-positive cells were assessed for the expression of the bystander marker of NKG2D and CD160. (B) The percentage of total bystander-phenotype-positive CD8⁺ T cells after stimulation with cytokine release syndrome (CRS)-associated cytokines and a paired t test was used for statistical analysis. (C) Percentage of total bystander-phenotype-positive CD8⁺ T cells with the bystander phenotype after titration of IL-2 and (D) IL-15. Stim, stimulated; unstim, unstimulated.