An optical method for the detection and quantitation of antibodies to glycosphingolipids and other antigens

Abstract

A simple, rapid technique has been developed for determining the optimal antibody-antigen ratio in complex formation between an antigen and its antibody. The technique makes use of the fact that complex formation is accompanied by an increase in light scattering. Complex formation was studied with two types of antigen, a protein (egg albumin) and a glycolipid (globoside). The glycolipid was present in the form of globoside-containing lecithin-cholesterol vesicles. The initial rate of complex formation was measured by following the change in optical density during the first few minutes of the reaction. When a constant amount of anti-egg albumin was used and the initial rate of complex formation with different amounts of antigen was plotted as a function of the antigen concentration, a maximum was obtained which coincided with the optimal antibody-antigen ratio in the precipitation technique. When a constant amount of globoside-containing liposomes was used, and the initial rate of complex formation with different amounts of antibody was plotted as a function of the antibody concentration, a maximum was obtained which coincided with the optimal antibody-antigen ratio in the radioimmunoprecipitation technique. With this technique, it is possible to determine the optimal antibody-antigen ratio in 1–2 hr, instead of the 1–2 days required for conventional techniques. The advantages of this technique are discussed with special reference to the detection of anti-glycolipid antibodies in bleedings during immunization, and to the detection of cross-reactivity between different antigens and antisera.