The authors carried out a comparative physico-chemical and immunochemical study of antigen obtained from the fraction of streptococcus cytoplasm by precipitation with ammonium sulfate, and partially purified M-protein. They proved to be heterogeneous by molecular-weight characteristics when tested by the methods of sedimentation analysis, disc-electrophoresis in polyacrylamide gel, and gel filtration on Sephadex G-200. Results of immunoelectrophoresis and disc-electrophoresis pointed to the presence in these two antigens of significant structural differences. A common component in M-protein and the cytoplasmic antigen was revealed by the immunodiffuse test. Spectrophotometric data pointed to the fact that M-protein represented protein, and cytoplasmic antigen was chiefly a nucleoproteid.
Antigens, Bacterial Cell Wall