Non-precipitating guinea-pig antibodies produced by administration of excessive doses of ovalbumin.

Partial paralysis of the antibody response in guinea-pigs produced by administration of an excessive dose of ovalbumin was accompanied by the formation of non-precipitating IgG1 and IgG2 antibodies. Immunochemical properties of these non-precipitating antibodies were compared with those of the precipitating antibodies obtained from animals given a normal dose of ovalbumin. Non-precipitating IgG2 antibodies did not fix complement and non-precipitating IgG1 antibodies elicited PCA but with less efficiency than precipitating IgG1 antibodies. On the other hand, the ammonium sulphate globulin precipitation technique for the determination of antibody affinity revealed that precipitating and non-precipitating antibodies were similar with regard to valency and average affinity for the antigen. These results are compatible with the hypothesis that non-precipitating antibodies result from a limited recognition of multiple antigenic determinants on ovalbumin molecules.