Solubilization of immune complexes in complement factor deficient sera and the influence of temperature, ionic strength and divalent cations on the solubilization reaction.
The complement-mediated solubilization (CMS) of immune complexes (IC) and the initial kinetics (IKS) of this reaction in human sera depleted of or deficient in C2, C3, C8, factors B, P and I were investigated. Sera depleted of B or P and those lacking native C3 or factor I showed virtually no CMS whereas the IKS and CMS capacity of a C8-deficient serum were within the reference range. The IKS of a C2-deficient serum was markedly retarded while the CMS capacity was normal. Addition of C2 normalized the kinetics of the reaction. There was a good correlation between the kinetics of CMS determined by a radioassay and kinetic data for the binding of C3b to preformed immune complexes. The CMS capacity reached maximum at 39-41 degrees C and at an ionic strength of approximately 0.20 mu. Selective chelation of Mg2+ completely abolished the CMS of IC. Maximal CMS was observed at Mg2+ concentration of about 2mM. Chelation of Ca2+ in serum by Mg2+-ethylene glycol tetraacetic acid reduced the CMS capacity by up to 50% and the IKS was markedly retarded. Varying the Zn2+ or Mn2+ ion concentrations in serum influenced neither the IKS nor the CMS capacity.
D000936:Antigen-Antibody Complex / Q000276:immunology*; D001665:Binding Sites; D002412:Cations; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003176:Complement C3 / Q000276:immunology; D003165:Complement System Proteins / Q000172:deficiency*; D006801:Humans; D007700:Kinetics; D009994:Osmolar Concentration; D012995:Solubility; D013696:Temperature
D000936:Antigen-Antibody Complex; D002412:Cations; D003176:Complement C3; D003165:Complement System Proteins