B Representative adhesion frequency (Pa) vs. contact duration (tc) curves forNKG2D expressing NK cells (n ≥ 3) in contact with RBCs (n ≥ 3) coated with a ligand (MICA in red, MICB in orange, ULBP1 in green, or ULBP3 in blue) at different contact durations, fitted by non-linear in-situ binding kinetics model Site densities of NKG2D (mr) and its ligands (ml) are indicated. Data information: Error bars are mean ± SEM for at least three independent biological experiments where *P < 0.05, **P < 0.01 (two-tailed unpaired t-test). 