Immunochemical Quantitation of IgG: Influences of the Antiserum and of the Antigenic Population

Purified IgG M-components of all subclasses and antisera raised against different populations of IgG or IgG Fc-fragments were used in an investigation of the influence of the antiserum and of the antigenic composition of the IgG population on the immunochemical quantitation of human IgG. Both the type of antiserum and the antigenic properties of the M-components were found to markedly influence the quantitation. Antisera against IgG Fc-fragments gave much better accuracy and reproducibility from antiserum to antiserum and from M-component to M-component than other antisera. The best antiserum (a rabbit antiserum against polyclonal IgG absorbed with Fab-fragments) gave values which were not influenced by the subclass of the M-component. IgGl(λ) M-components were found to give slightly higher values than IgGl(x) M-components with all antisera used.