The reactivity of the antiserum is directed to the Fc subunit of the IgG molecule which expresses The reactivity of the antiserum is directed to the Fc subunit of the IgG molecule which expresses tested by immunoelectrophoresis and double radial immunodiffusion. As unlabelled primary or secondary reagent for indirect detection of IgG at the cellular and subcellular level by staining of appropriately treated cell and tissue substrates; to prepare conjugates of the user’s own choice; to prepare an insoluble immunoaffinity adsorbent or a solid phase antibody reagent by coupling to an artificial carrier and as catching antibody in nonisotopic methodology and solid phase immunochemistry. When applied in any cytochemical or histochemical staining procedure or solid phase coupling technique, the optimum concentration of the IgG preparation should be established by titration before being used.