Comparison of pH and ionic strength dependence of interactions between monoclonal antibodies and bovine beta-Lactoglobulin

A panel of 13 monoclonal antibodies (mAbs) against distinct determinants on bovine beta-lactoglobulin, a model protein antigen, were examined and compared for their ability to bind and desorb from the antigen at differing pHs and ionic strengths by an enzyme-linked immunosorbent assay and elution assay. Among them, mAb 61Cl was found to be highly sensitive to the pH, and 3 in 4 mAbs directed to the region 42-56 also strongly depended on the change in ionic strength. Because of the large proportion of charged amino acid residues in the region 42-56, the electrostatic forces are considered to be more predominant than the hydrophobic interactions in the latter antigen-antibody reactions, thereby resulting in their high sensitivity to the ionic strength.