Composition and Biologic Properties of Soluble IgG-Anti-IgG Immune Complexes: Effects of Variations in the Specificity of Rabbit Antibodies to Different Structural Components of Human IgG

摘要

Rabbit antibodies specific for antigenic determinants on the Fab fragments, Cγ2 domain, or Cγ3 domain of human IgG were purified by affinity chromatography. The interaction of these purified IgG antibodies with whole human IgG as antigen was examined. Antigen and antibody preparations were utilized that possessed either intact or reduced and alkylated interchain disulfide bonds. Quantitative precipitin analyses showed that the degree of precipitation, when antibodies were combined with antigen at equivalence, varied between the three antibody preparations. The Fab-specific antibodies gave the highest precipitability with the Cγ2-specific antibodies being intermediate and the Cγ3-specific antibodies exhibiting the least precipitation. In general, reduction and alkylation of either the antigen or antibodies, or both, led to a decrease in the amounts of antibodies precipitated at equivalence. In spite of the differences in precipitability at equivalence, soluble complexes prepared in 3-fold antigen excess possessed comparable amounts of larger-latticed structures (Ag2Ab2) in each antigen-antibody system. However, the relative amounts of small-latticed complexes present were greater with the Fab-specific antibodies.The biologic properties of soluble IgG-anti-IgG complexes were evaluated with the antibody preparations of different specificities. The human IgG antigen in the complexes containing Fab-specific antibodies contributed to the ability of the complexes to activate complement and to bind to macrophage Fc receptors. In contrast, the IgG antigen in the complexes containing Cγ2- or Cγ3-specific antibodies was inhibited from contributing to these biologic activities.It was concluded that the specificity of antibodies to IgG has significant effects on the interaction with antigen and on the biologic properties of soluble IgG-anti-IgG complexes.