Evaluation of polyethylene glycol's suitability for quantitative determination of non-precipitating antibody

Polyethylene glycol (PEG) has been used extensively in the quantitative precipitin reaction and for the determination of soluble immune complexes. It has now been found that the optimum concentration of PEG for precipitation of non-precipitating antibodies in the quantitative precipitin reaction varies with the dilution of antisera. Immune precipitates obtained with PEG were examined for their protein content by polyacrylamide gel electrophoresis to detect non-specific precipitation of serum proteins. Determination of non-precipitating antibodies in sera of goats and pigs immunized with chicken egg-white lysozyme by the quantitative precipitin reaction in the presence of PEG, yielded lower values than obtained by immunoabsorbents. Care should be exercised in interpreting results when PEG is used to enhance precipitation.