FLOW-INDUCED DETACHMENT OF RED-BLOOD-CELLS ADHERING TO SURFACES BY SPECIFIC ANTIGEN-ANTIBODY BONDS

Fixed spherical swollen human red blood cells of blood type B adhering on a glass surface through antigen-antibody bonds to monoclonal mouse antihuman lgM, adsorbed or covalently linked on the surface, were det ached by known hydrodynamic forces created in an impinging jet. The dy namic process of detachment of the specifically bound cells was record ed and analyzed. The fraction of adherent cells remaining on the surfa ce decreased with increasing hydrodynamic force. For an lgM coverage o f 0.26%, a tangential force on the order of 100 pN was able to detach almost all of the cells from the surface within 20 min. After a given time of exposure to hydrodynamic force, the fraction of adherent cells remaining increased with time, reflecting an increase in adhesion str ength. The characteristic time for effective aging was approximately 4 h. Results from experiments in which the adsorbed antibody molecules were immobilized through covalent coupling and from evanescent wave li ght scattering of adherent cells, imply that deformation of red cells at the contact area was the principal cause for aging, rather than loc al clustering of the antibody through surface diffusion. Experiments w ith latex beads specifically bound to red blood cells suggest that, in stead of breaking the antigen-antibody bonds, antigen molecules were e xtracted from the cell membrane during detachment.