A comparative study of the immunogenicity of some penicillins and of their cross reactions.

The immunogenicity of four penicillin preparations was comparatively investigated by titration of penicilloyl (PO) specific hemagglutinating antibodies found in sera of rabbits inoculated with equimolecular amounts of these penicillins incorporated in Freund incomplete adjuvant. Benzylpenicillin (BP) was shown to be endowed with the highest immunogenicity, while oxacillin (OX), ampicillin (AM) and Amoxil (AX) were found significantly less immunogenic. By examining comparatively the titers of hemagglutination reactions given by the sera of each animal with erythrocytes coated with the penicillin used for its immunization as well as with the other penicillins investigated, important cross immunological reactions were found in all of the cases. Interestingly, the cross reactions produced by AM- and AX-specific antisera with heterologous penicillins were apparently higher than the reactions obtained with the homologous penicillin. No significant differences were found concerning the ability of the four penicillins to form PO conjugates with BGG. Thus, the differences in immunogenicity exhibited by the four penicillin preparations may not be explained in this way.