Dissociation of Antibody from Erythrocyte Surfaces by Chaotropic Ions

Abstract

Abstract IgG, Fab′ and IgM antibodies may be effectively dissociated and partitioned from their homologous erythrocyte surface antigens by chaotropic ions. The efficacy of dissociation of antibody is proportional to the chaotropic properties and molar concentration of the ions in the order SCN- τ; I- τ; Cl-. Complete dissociation of 125I-labeled Fab′ anti-erythrocyte antibody can be achieved with moderate concentrations of iodide and thiocyanate. Disruption of antigen-antibody bonds by chaotropic ions is more readily achieved from cell membrane antigens than from solid immunoadsorbents containing a relatively stable antigen such as human IgG. At chaotropic ion concentrations required for maximal dissociation of antibody, significant irreversible denaturation of membrane antigens, but not of antibody or serum protein antigens, is observed. Conformational changes in membrane antigens, possibly resulting from displacement of hydrophobic forces by chaotropic ions, may contribute to the more effective dissociation of antibody from some cell membrane antigens. Purified 125I Fab′ antibodies exhibit specific primary binding and, because of their univalent nature, may be utilized for quantitative and qualitative elucidation of cell surface antigens. The similarity of equilibrium constants observed with differing erythrocytes of similar Rh phenotype suggests a considerable degree of similarity, if not absolute identity of, the D (Rh0) antigen in different individuals. It also appears that these antigen sites are widely spaced on the erythrocyte surface.