Heterogeneity in antibody production is a hot topic in the biological drug discovery business these days. It has long been known that production of antibodies in cell culture can lead to variation in antibody structure. However, it has yet to be shown that these variations truly have an effect in antibody structure and function in immunological assay or in circulating plasma. In a series of publications, Amgen scientists have conclusively demonstrated that circulating human IgG2 antibodies isolated from myeloma patients and normal serum appear to be a naturally occurring feature of antibodies belonging to the human igG2 subclass. (Wypych et. al 2008). In particular, they report the effects of disulfide bond heterogeneity, which can presumably affect antigen binding affinity and avidity and possibly affect the immune function at an organismal level. While binding activity assays of the human IgG2 monoclonal antibody did not appear to be effected, this was not the case in an accompanying study (Dillon et. al 2008). In this accompanying report, they noted that disulfide mediated heterogeneity was indeed able to affect structure and function, which was manifested in several cell-based assays.
While the group was able to partially purify the antibodies on cation exchange columns to pursue their functions, they noted that further studies were necessary to fully characterize these variations in antibody structure. However, purification of these isoforms can be somewhat daunting. This is where the SACHEM approach of purification of antibody variants using displacement chromatography to isolate and concentrate the charge variants can be very useful. In fact, this approach has been used to generate quantities of these variant antibodies for pharmacokinetic studies in animals (Khawli et. al. 2010). So for antibody groups who are looking for ways to conclusively nail antibody heterogeneity issues, displacement offers a unique and robust approach to solving these problems.