immunodiffusion assay radial immunodiffusion assay 2013-11-13T15:01:23Z A technique used to determine the quantity of an antigen by measuring the diameters of circles of precipitin complexes surrounding samples of the antigen that mark the boundary between the antigen and an antibody suspended in a gel. Antigen diffuses into the gel matrix containing a specific antibody and a ring of precipitate is formed, the diameter of which is directly proportional to the concentration of the antigen. Precipitin is an antibody that has specifically aggregated a macromolecular antigen to give a visible precipitate. JSmith MMO:0000439 Mancini immunodiffusion Mancini method measurement_method_ontology single radial immunodiffusion assay