Determination of adhesive specific energy of erythrocyte agglutination by laser retrodiffusion

The quality of an antibody is related to its affinity expressed by the equilibrium constant. The biological activity of an antibody can be estimated by the strength of antigen–antibody bridges.

An optical method is proposed to estimate the specific binding energy using the dissociation behavior of suspended RBC agglutinates in a shear flow and measuring laser backscattering. A constant increase of intensity was observed when the shear stress raises, pointing to a progressive dissociation of RBC agglutinates into smaller ones. The final break-up of two-cell rouleaux is produced at critical shear stress (τ_c), which reflects the mechanical action required to dissociate the molecular bridges between cells. The critical shear stress permitted to define the specific surface adhesive energy (Γ) by using the Derjaguin relation. The determination of τ_c provides a good way to assess the functional characterization of specific immunoglobulins, which could be very useful for antibody quality control.