An indirect antibody assay using haptenated antigen and 125i-labelled anti-hapten antibody.

Hapten (trinitrophenyl) was coupled to antigen (ovalbumin). The haptenated antigen was bound by anti-ovalbumin antibody and binding was quantitated with 125I-labelled anti-hapten antibodies. Thus, with a single radioactive reagent antibodies against a variety of antigens can be detected, whilst the problems inherent in a labelled antiglobulin binding test are avoided. In the ovalbumin system, the haptenated antigen binding test proved to be approximately 20 times as sensitive as the iodinated ovalbumin binding test.