Detection of antibodies against Streptococcus mutans cell wall contaminating sera against ribosomal fractions

A modification of the immunoprecipitation technique was developed to precipitate ribosomal proteins from Streptococcus mutans in isoelectric focusing gels. The method was established in order to determine whether the ribosomal immunogen was contaminated with cell surface proteins. Isoelectric focusing was used to separate the proteins into bands in the gel and various antisera utilized to precipitate the antigens. Electrophoresis of the ribosomal preparation produced 19 protein bands. A rat antiserum raised against the preparation reacted with 8 of these bands and an aliquot of the same antiserum which had been adsorbed with whole S. mutans cells reacted with only 6 bands. This procedure allowed us to detect contamination of the ribosomal preparation with cell surface antigens. The method may be used to detect contamination with cell surface antigens in many different subcellular preparations.