Simple hanging drop (20 μl) double antibody radioimmunoassay of human IgM, IgG, IgA, IgD and IgE

A simple hanging drop radioimmunoassay has been developed for different classes of human immunoglobulin from serum or culture supernatant samples. The immune precipitate was formed in inverted Terasaki plates (20 μl per well) using 4 aliquots (5 μl) as follows: (A) a standard or unknown sample; (B) rabbit antisera to the appropriate immunoglobulin class; (C) 125I-labelled human immunoglobulin of the appropriate class; (D) a developing goat-anti rabbit serum. The immune precipitate in the hanging drop was harvested and washed without centrifugation with a simple Terasaki plate harvester. The method gives a great saving both in time and in sample and reagent volumes in comparison with an established double antibody assay in tubes (4 x 100 μl aliquots). (Auth.)