Agglutination microassay of hapten- or protein-modified liposomes using a multiple cell culture harvester

A simple agglutination microassay is described for studying the presence of antigenic determinants on the surface of liposomal membranes. Antigen-sensitized radioactive liposomes, reacted with specific immune IgG in the wells of a microtest plate, were passed through a glass fiber filter in a multiple cell culture harvester. The amount of agglutinate trapped on the filter as determined by the radioactivity, was proportional to the amount of antigen in the liposomes and to the amount of specific immune IgG in the reaction mixture. The specificity of the agglutination was determined by inhibition with hapten and carrier antigens. Liposomes actively sensitized with hapten-conjugated lipid, and passively sensitized with protein, were used in the assay. A new method of preparing protein-bound liposomes is also described.