Changes induced in antibodies by isolation methods.

IgG was isolated from plasma at low temperatures using the Cohn fractionation method, and then processed to three different products in order to evaluate how chemical and physical manipulations affect antibodies. Evaluation of the antibodies was done by measuring their ability to bind human immunodeficiency virus, cytomegalovirus, Herpes simplex virus, and rubella virus. In addition, the IgG products were compared by crossed immunoelectrophoresis, and circular dichroism and ultra violet spectroscopy. It was found that exposure of purified IgG to physiological pH altered the molecular conformation of IgG and induced various degrees of irreversible loss in antibody binding to viruses. These observations indicate that more efficacious antibodies may be obtained for clinical use if isolation at their isoelectric point is avoided.