Complement-mediated fragmentation of soluble and insoluble immune complexes containing porcine anti-DNP antibodies

Complement-mediated release of soluble immune complexes and immune precipitates containing DNP-PSA and precipitating or non-precipitating porcine anti-DNP antibodies was studied. A decrease in the average size of soluble immune complexes indicating their fragmentation was observed during incubation in excess human serum, the extent of the complex release was found to be in direct proportion to the time of incubation. The effect was complement-dependent. In the second part of the study, complement-dependent solubilization of the immune precipitates of the precipitating antibody preparation was compared to the solubilization of the precipitates of the non-precipitating antibody formed in the presence of PEG. Although, both types of precipitates activated complement in about the same extent, complexes of non-precipitating antibody were solubilized much slower than those of the precipitating one. As avidity of both antibody preparations to the antigen was high, the observed differences in the rate of the complex solubilization probably reflected differences in the structure of the two types of complexes.