Soluble M1 Protein of Streptococcus Pyogenes Triggers Potent T Cell Activation

Cell Microbiol. 2008 Feb;10(2):404-14. doi: 10.1111/j.1462-5822.2007.01053.x. Epub 2007 Sep 28.


Streptococcus pyogenes of the M1 serotype is commonly associated with large outbreaks of invasive streptococcal infections and development of streptococcal toxic shock syndrome (STSS). The pathogenesis behind these infections is believed to involve bacterial superantigens that induce potent inflammatory responses, but the reason why strains of the M1 serotype are over-represented in STSS is still not understood. In the present investigation, we show that a highly purified soluble form of the M1 protein from S. pyogenes, which lacks the membrane-spanning region, is a potent inducer of T cell proliferation and release of Th1 type cytokines. M1 protein-evoked T cell proliferation was HLA class II-dependent but not MHC-restricted, did not require intracellular processing and was Vbeta-restricted. Extensive mass spectrometry studies indicated that there were no other detectable proteins in the preparation. Taken together, our data demonstrate that soluble M1 protein is a novel streptococcal superantigen, which likely contributes to the excessive T cell activation and hyperinflammatory response seen in severe invasive streptococcal infections.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Bacterial / immunology*
  • Bacterial Outer Membrane Proteins / immunology*
  • Carrier Proteins / immunology*
  • Cell Line
  • Cell Proliferation
  • Cytokines / immunology
  • Histocompatibility Antigens Class II / immunology
  • Humans
  • Lymphocyte Activation*
  • Mass Spectrometry
  • Receptors, Antigen, T-Cell / immunology
  • Streptococcus pyogenes / immunology*
  • T-Lymphocytes / cytology
  • T-Lymphocytes / immunology*
  • Th1 Cells / immunology
  • Virulence Factors / immunology*


  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Cytokines
  • Histocompatibility Antigens Class II
  • Receptors, Antigen, T-Cell
  • Virulence Factors
  • streptococcal M protein