NKp80-AICL interactions enhance alloreactive CD8 T-cell responses. (A, left) 293T-AICL transfectants broadly express AICL at the cell surface and bind soluble NKp80. Staining of 293T-AICL with anti-AICL mAb 7F12 (black histogram) and isotype control (dashed line) overlaid with staining of 293T-neo (7F12 [gray histogram]; isotype control [dotted line]). (A, right) Tetramers of soluble NKp80 ectodomains bind to 293T-AICL (black histogram) but not to 293T-neo (gray histogram). (B,C) Purified CD8⁺ cells were cocultured with irradiated 293T-neo or 293T-AICL in the presence of IL-2 and, where indicated, of anti-NKp80 5D12 or control IgG1. After 8 days of coculture, cells were restimulated with 293T-neo or 293T-AICL cells and CD107a expression of CD3⁺ cells was analyzed with flow cytometry. (B) Representative dot plots for donor 1. (C) Means and standard deviations of triplicates for donors 1, 2, and 3. (D) Enhanced cytolysis of 293T-AICL by alloreactive NKp80⁺ CD8⁺ T cells. NKp80⁺ and NKp80⁻ subsets of effector memory T cells (CCR7⁻CD8⁺CD3⁺) were sorted with FACS from purified CD8⁺ cells, cocultured with irradiated 293T-neo for 10 days, and subsequently used as effector cells in chromium release assays with 293T-neo and 293T-AICL, respectively, as target cells.