Direct measurement of IgM-Antigen interaction energy on individual red blood cells

Most blood grouping tests rely on the principle of red blood cells (RBCs) agglutination. Agglutination is triggered by the binding of specific blood grouping antibodies to the corresponding RBC surface antigen on multiple cells. The interaction energies between blood grouping antibodies and antigens have been poorly defined in immunohaematology. Here for the first time, we functionalized atomic force microscope (AFM) cantilevers with the IgM form of blood grouping antibodies to probe populations of individual RBCs of different groups under physiological conditions. The force-mapping mode of AFM allowed us to measure specific antibody – antigen interactions, and simultaneously localize and quantify antigen sites on the scanned cell surface. This study provides a new insight of the interactions between IgM antibodies and its corresponding antigen. The technique and information can be translated to develop better blood typing diagnostics and optimize target-specific drug delivery for medical applications.