Sera from ragweed-sensitive individuals (two untreated and six treated) were examined by radioimmunoelectrophoresis to detect and identify the serum components possessing the binding activity for a purified fraction of ragweed (ragweed-binding antibodies). The method utilizes the fixation of I131-labeled ragweed antigen on the arcs formed by electrophoresed human antibody components and rabbit anti-human serum.
The ragweed-binding activity was detected in the γ-globulin of all the sera and in the β2A-globulin of all but one serum. Two sera showed the activity also in the β2M-globulin. In fact, all the sera contained the activity in the β2A- or in the β2M-globulin in addition to the activity in the γ-globulin. (One serum contained the activity in all three globulins, γ, β2A and β2M.) Such a high incidence of the β2A or β2M-antibody in sera of sensitive individuals suggests the association of the reaginic activity with these antibodies.
The ragweed-precipitating antibodies were detected in the γ2-globulin region of some sera including one from an untreated individual. The precipitating antibodies, when present in large amounts, interfered with the identification of antibody components. A modified technique, applicable to such precipitating systems, was described.