Radioimmunoassay in microtiter plates. A convenient method for determining bound radiolabelled ligand

A radioimmunoassay was performed in the wells of casein-coated microplates employing 125I-labelled sheep anti-human second antibody. The antigen-antibody complexes were thereafter dislodged from the well walls using the detergent sodium dodecyl sulfate (SDS) and the entire contents of the wells were simultaneously absorbed into 48 cellulose acetate-absorbing cartridges. All 48 cartridges were transferred to counting vials and the radioactivity determined by standard gamma counting techniques. The particular advantage of the method described here is the ease with which the supernatants can be collected and transferred to counting vials with minimal handling of radioactive samples.