SPR sensograms for the interaction of wild-type 2B4 (225, 112, 56, 33.8, 28.2, 16.9, 14.1, 7.0, 3.5, 1.8 μM) (A) and 2B4 E91A mutant (552, 276, 138, 69, 55.2, 34.4, 27.6 μM) (B) with immobilized CD48 (700 RU) after correction for nonspecific binding. Inset plots show non-linear steady-state affinity analysis of the equilibrium binding data. KD = 4 μM for wild-type 2B4; KD = 130 μM for 2B4 E91A.