Down-regulation of CD16 and CD62L surface expression upon activating receptor cross-linking. (A-B) Purified NK cells (n = 7) were cross-linked with plates adsorbed with IgG or antibodies to CD16, 2B4, 2B4, and CD16, 2B4 and NKp46, 2B4 and DNAM-1, NKG2D and NKp46, NKp46 and CD2, or NKG2C. Purified NK cells were also stimulated with K562 cells. Intracellular IFN-γ (A, left panel), TNF-α production (A, right panel) and surface expression of CD16 (B, left panel), and CD62L (B, right panel) were measured after 5 hours. NE, not evaluable. Bars represent mean ± SEM. Cytokine production and percentage of CD16 and CD62L expression were compared with the isotype control using the paired t test. Statistical significance is indicated as: *P ≤ .05; **P < .01; ***P < .001. (C) The percentages of CD56^dim NK cells producing IFN-γ (left panel) or TNF-α (right panel) after cross-linking with plate bound antibodies were plotted against the percentage of CD62L expression. Each point represents an individual result against 1 activating receptor. The estimated regression line is shown with the r value and significance based on the Pearson correlation coefficient. Significance is calculated as P < .05.