Expression of NK receptors in naive CD8⁺, but not CD4⁺, T cells after TCR stimulation. (A-D) A total of 0.2 to 1 × 10⁵ unlabeled (A-B,D) or CFSE-labeled (C) purified naive CD8⁺ (A-D) or CD4⁺ (D) T cells purified from 2C TCR Tg (A-C) and B6 (D) mice were stimulated with either plate-bound anti-CD3 monoclonal antibody (1-10 μg/mL; A-D) or PMA (50 ng/mL) plus ionomycin (500 ng/mL) (PMA/Iono; A,D) and analyzed on day 3 (A-B), days 1 to 3 (C), and day 2 (D) for the indicated activation markers (CD44 and CD25; A,C) and NK-cell receptors (CD94, NKG2A, NKG2ACE, and NKG2D; A-D) by flow cytometry. The percentages of cells in the respective regions (A,C) are indicated. (A-D) Data are representative of at least 3 independent experiments (B,D; mean ± SD).