Italics indicates an inhibitory receptor. Normal text indicates an activating receptor. Rankings are based on K_A x10⁵M⁻¹ for each interaction reported in published studies [1],[5],[6]. ++++ indicates a K_A greater than 100 x 10⁵ M⁻¹, +++ indicates a K_A between 20 and 99 x 10⁵ M⁻¹, ++ indicates a K_A between 1 and 19 × 10⁵ M⁻¹, + indicates a K_A between 0.5 and 0.9 × 10⁵ M⁻¹, − indicates a K_A that was undetectable or less than 0.5 × 10⁵ M⁻¹ .