Recovery of monoclonal antibody from its complex with ligand.

The separation of antibody from its excess and bound ligand is important following affinity chromatography or the use of methods requiring large amounts of antibody, such as microcalorimetry. Using radioactively labeled ligands we show that these separations can be effected by using commercially available, short polyacrylamide size-exclusion columns. By using both low (K alpha = 5 x 10(2) M-1) and medium high-affinity (K alpha = 0.6 x 10(6) M-1) ligands in the presence of antibody, it is shown that the latter system requires more dilute loading concentrations than the former system does in order to achieve acceptable separation. Since the degree of association between a protein and a ligand is solely governed by the affinity constant for the binding equilibrium, these results are applicable to any system represented by this range of binding constants.