NKp80⁺ CD8 T cells are potent effectors. (A,B) Enhanced expression of cytotoxic effector proteins perforin and granzyme B by NKp80⁺ CD8 T cells. Flow cytometric analysis of freshly isolated PBMCs gated on CD3⁺CD8⁺ cells for coexpression of NKp80 and intracellular perforin or granzyme B, respectively. (A) Representative dot plot analysis of 1 donor and (B) compiled MFI data for 8 healthy donors are shown. Lines indicate MFI values derived from same donors. (C,D) High responsiveness of NKp80⁺ CD8 T cells. Freshly purified CD8⁺ cells were stimulated with PMA/ionomycin for 6 hours and stained for CD107a or intracellular IFNγ in conjunction with NKp80. CD3⁺CD8⁺ T cells were gated for flow cytometric analysis. Dot plots (C) and means and standard deviations (D) of triplicates for one representative donor. Similar results were obtained with 2 other donors (not shown). (E) Multiple cytokine expression by NKp80⁺ CD8 T cells. Freshly isolated PBMCs were stimulated with PMA/ionomycin for 6 hours and simultaneously stained for intracellular IFN-γ, TNF, and IL-2. CD3⁺CD8⁺CCR7⁻ T cells were gated for flow cytometric analysis of cytokine expression by NKp80⁺ and NKp80⁻ cells, respectively. Means and standard deviations of frequencies of T-cell subsets expressing different combinations of cytokines are shown for 1 representative donor. Similar data were obtained with 3 other donors. (F) Fresh PBMCs were stained with CFSE and cultured for 8 days in the presence of IL-2, IL-7, and IL-15. On day 8, NKp80⁺CD3⁺ and NKp80⁻CD3⁺ cells were gated (left) and analyzed for CFSE levels (right). Data are representative of 5 experiments.