Ferritin-labeling of antibodies by glutaraldehyde. Comparison of conjugates prepared at different antibody: ferritin: glutaraldehyde ratios

Isolation of model soluble immune complexes in the fluid phase by monoclonal anti-IgG-ferritin antibodies

Ferritin conjugates of monoclonal IgG anti-human gamma chain (anti-IgG-F) were reacted with soluble heat aggregates of IgG (A-IgG) and with soluble DNA-anti-DNA complexes to increase the S rate of the model soluble immune complexes (ICx) and thus facilitate isolation of ICx in the fluid phase and provide an immunochemical marker for subsequent ultrastructural analysis. A-IgG appeared as globular or curvilinear structures with individual IgG molecules arranged in a random fashion. The technique appears promising for characterization of other soluble ICx.

Optimal conditions for the preparation of ferritin-labeled antibodies defined by binding to their antigen in an ELISA

An ELISA with covalently fixed antigens was used to measure and define ferritin-labeled antibodies. In the presented model, RIG covalently fixed to glass tubes served as antigen. Twenty ferritin-labeled SWaRIG conjugates were prepared with different molar ratios of antibody: ferritin: glutaraldehyde. At various dilutions, their ability to react with the antigen was compared. The amount of FRT in the reactive conjugates was measured using alkaline phosphatase-labeled antibodies against ferritin. The covalent binding of antigens to glass surfaces resulted in a low unspecific binding as shown previously. Besides, these glass tubes with antigens immobilized on their inner surface could be used more than once. This aspect of it renders this test particularly suitable for systems where rare or expensive antigens are used. The range of O.D. values reflecting the amount of reactive SWaRIG/FRT detected in 20 different conjugates (dil 1:1000) was spread over a good range which allowed a specification of optimal conditions for FRT labeling of antibodies. It is concluded that in addition to an electron microscopic evaluation of the conjugates, this assay may be very helpful in defining optimal conditions for the coupling procedure.