Effect of polyethylene glycol on the rate of immune complex formation by non-precipitating antibody

A kinetic study formation of large size complexes of non-precipitating pig-Dnp anti-Dnp antibody and multivalent dinitrophenylated serum albumin was performed using light scattering and absorption spectroscopy of the Dnp-group. A very rapid phase of the process resulted in the formation of complexes having molecular weight of about 2 × 10 6 . Further increase of the complex size was much slower. Addition of PEG affected positively the rate of complex growth even in concentrations below 1%. The spectroscopic kinetic curves also showed a rapid and a slow phase, sensitive to the presence of PEG. The character of the kinetic data does not support the simple view that polymers enhance precipitate-formation by the steric exclusion of complexes from the polymer domains. It can be assumed that the interaction of the polymer with the antigen-antibody system consists of a subtle temporary attachment of the polymer to the antibody molecule resulting in a change of the shape and/or flexibility of the antibody molecule, favouring its cross-linking capacity.