Binding of holoTC and apoTC by anti-human TC mAbs. (A) SPR sensorgram of the binding of mAb 3C4 to immobilized recombinant holoTC and apoTC. HoloTC and apoTC were first bound to mAb 3–11, which was covalently attached to the sensor chip, and then mAb 3C4 was injected over the sensor chip. (B) The affinity and specificity of seven different antibodies for native holoTC and apoTC. The Figure depicts one experiment using quadruplicate assays. Antibodies were immobilized on paramagnetic microspheres. See Material and Methods. (C) Binding of 57Cbl holoTC to mAb 3C4 and mAb 3–9 as a function of pH. (D) Binding of 57Cbl holoTC to mAb 3C4 and mAb 3–9 as a function of ionic strength at pH 7.3.