648 Coupling Protein Antigens to Ei

A method has been described whereby tuberculin P P D is linked to formalinized erythrocytes by a coupling agent, tetrazotized benzidine (1). These antigen-coated erythrocytes are agglutinated by ant ibody to PPD. I t was observed that P P D could inhibit the hemagglutination more effectively than could polysaccharide I. I t appears, therefore, tha t the ant ibody concerned is directed toward the protein portion of the tubercle bacillus. This antigen-antibody system is presumably different from that measured by the Middlebrook-Dubos technique (2). In the latter, polysaccbaride I effects inhibition more strongly than does tuberculoprotein; and the ant ibody involved appears to be directed toward a polysaccharide antigen (3). The present s tudy deals with the use of the sensitized, formalinized red cells for the diagnosis for tuberculosis. The stability of the antigen preparation, and the omission of an adsorption procedure to remove isoagglutinins contribute to the simplicity of the method.