title: The specificity of a solid phase radioimmunoassay for human immunoglobulins.
abstract: The specificity of a solid phase radioimmunoassay for immunoglobulin antigens, human Fab-mu in the case illustrated, has been assessed. The anti-Fab-mu serum available reacted well on gel diffusion with all Fab-mu- and light chain-containing proteins. In contrast the radioimmunoassay, in which unlabelled test antigen competes with radiolabelled Fab-mu for anti-Fab-mu coupled to Sephadex beads, was sensitive only to proteins containing entire Fab-mu regions. A double antibody radioimmunoassay showed comparable or greater sensitivity for Fab-mu-containing proteins, but was much less specific. By using Fab-gamma as the labeled antigen, with only light chain determinants reacting with the anti-Fab-mu, the solid phase assay was rendered polyspecific in being sensitive to all proteins containing light chain. Reasons for the specificity of the solid phase assay are discussed: steric factors can be expected in some cases to permit strong binding of antigen by multiple bonds, in others to restrict the number of molecular determinants simultaneously available to antibody.
mesh_terms: D000645:Ammonium Sulfate; D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins; D002848:Chromatography, DEAE-Cellulose; D000939:Epitopes; D006454:Hemoglobins; D006736:Horses / Q000276:immunology; D006801:Humans; D007106:Immune Sera; D005779:Immunodiffusion; D007140:Immunoglobulin Fab Fragments / Q000032:analysis; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G / Q000302:isolation & purification; D007143:Immunoglobulin Heavy Chains / Q000032:analysis; D007136:Immunoglobulins / Q000032:analysis*; D007457:Iodine Radioisotopes; D011817:Rabbits / Q000276:immunology; D011863:Radioimmunoassay / Q000379:methods*
chemical_list: D002352:Carrier Proteins; D000939:Epitopes; D006454:Hemoglobins; D007106:Immune Sera; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007136:Immunoglobulins; D007457:Iodine Radioisotopes; D000645:Ammonium Sulfate