Immune-complexes solubilization: effect of antigen-antibody ratio and relative role of alternative and classical complement pathways.
Insoluble immune-complexes (IC) are solubilized by complement. A functional alternative pathway (AP) is required for solubilization. Classical pathway (CP) has an enhancing effect, but the effect of antigen-antibody (Ag-Ab) ratio and the relative role of AP and CP at these different Ag-Ab ratios is controversial. We reinvestigated these factors in a human model (IC prepared with tetanus toxoid and affinity purified human Ab solubilized by normal serum--NHS). We present evidence that (1) IC prepared at Ag excess are only partially solubilized. (2) IC prepared at large Ag excess are not solubilized by AP. (3) AP prepared at Ab excess are solubilized exclusively by AP. (4) IC prepared at equivalence are solubilized by AP and CP acting in synergy.
D000936:Antigen-Antibody Complex; D001769:Blood; D003167:Complement Activation; D003170:Complement Pathway, Alternative; D003171:Complement Pathway, Classical; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007700:Kinetics; D008970:Molecular Weight; D012995:Solubility; D013745:Tetanus Toxoid / Q000276:immunology
D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D013745:Tetanus Toxoid