The inhibition of the primary interaction between 1 2 5I-labeled human hemoglobin and rabbit anti-human hemoglobin sera: A sensitive radioimmunoassay technique

Abstract

A rapid and sensitive radioimmunoassay technique for hemoglobin based upon a modification of the Farr test is described. Since hemoglobin is soluble in ammonium sulfate whereas antibody is precipitated, the amount of free and antibody-bound radiolabeled human hemoglobin can be quantitatively measured after ammonium sulfate precpitation. Nanogram quantities of hemoglobin can be detected by the addition of unlabeled human hemoglobin to the antiserum before the labeled hemoglobin, thus establshing a competition reaction between labeled and unlabeled antigen for antibody. If sufficient quantities of unlabeled human hemoglobin are present, all of the antibody combining sites become saturated and the primary interaction between 1 2 5I-labeled hemoglobin and antibody is completely inhibited. The method can be employed to discriminate various normal human hemoglobins, non-human primate hemoglobins as well as sickle-cell hemoglobin (HbS). Other possible applications of the technique are discussed.