CD7⁺ NK cells do not induce allogeneic T-cell proliferation in a mixed leukocyte reaction. PBMCs were purified by flow cytometry into 4 populations: classical NK cells (CD3^negCD56⁺), CD7⁺CD56⁺ NK cells, CD7^negCD56⁺ DCs/monocytes, and CD14⁺ and CD19⁺ antigen-presenting cells. (A) Flow cytometry–purified cells were γ-irradiated and incubated in a 1:1 ratio with CFSE-labeled allogeneic T cells. After incubating for 7 days, cells were analyzed for dilution of CFSE as a marker of proliferation. PHA-stimulated T cells were used as a positive control. One representative donor (n = 3) is shown. Similar results were also obtained when the reaction was performed in the presence or absence of 250 IU/mL of IL-2. (B) Flow cytometry–purified cells (1000 per well) were added to wells containing media alone, lipopolysaccharide (LPS), IL-12 + IL-18, or poly(I:C) for 18 hours. One representative experiment of 3 is shown.