Separating antibody species containing one and two kappa light chain constant region by KappaSelect affinity chromatography

KappaSelect is an affinity medium that specifically binds to the constant region of the kappa light chain (LC). Obviously, KappaSelect can be used to separate antibody species containing the kappa LC constant region from those lacking that region. However, it is not clear whether this resin can readily separate species containing one kappa LC constant region from those containing two kappa LC constant regions although the former are assumed to bind weaker than the latter. In this work, we demonstrated that antibody species with two kappa LC constant regions binds to the KappaSelect resin much tighter than species with only one kappa LC constant region. Consequently, these two species can be readily separated using this resin. This information not only enriches our knowledge with KappaSelect but also has important practical value. In addition to the sample case used in the current study, there are other cases in which the target protein contains one kappa LC constant region whereas a byproduct contains two kappa LC constant regions. Our finding provides a convenient means for removing such two kappa LC binding site containing byproduct in these cases.