title: Superantigenicity of helper T-cell mitogen (SPM-2) isolated from culture supernatants of Streptococcus pyogenes.
abstract: A superantigen (Streptococcus pyogenes mitogen-2; SPM-2) that stimulates human helper T cells bearing unique types of variable domains of T-cell receptor beta-chain (TCR V beta) was isolated from the culture supernatant of S. pyogenes strain T12. The active molecule isolated by diethylaminoethyl (DEAE)-cellulose chromatography and isoelectric focusing was a protein with a molecular weight (MW) of 29,000 and isoelectric point (pl) of 6.0. This new superantigen was found to activate preferentially V beta 4+, 7+, and 8+ T cells, whereas recombinant streptococcal pyrogenic exotoxin A and C activated V beta 12+ and V beta 2+ T cells, respectively, as determined by flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR) methods. This proliferative response was significantly inhibited by anti-HLA-DR monoclonal antibody, and required paraformaldehyde-fixed antigen-presenting cells (APC), indicating that this action is dependent on major histocompatibility complex (MHC) class II molecules without processing. Analysis of the amino-terminal amino acid sequence of the molecule failed to find any identical or significantly homologous proteins. We have previously reported that cytoplasmic membrane-associated protein (CAP), a streptococcal superantigen isolated from the cell membranes of S. pyogenes T12 strain, stimulated mainly V beta 8+ T cells. Both SPM-2 and CAP preferentially stimulated helper T cells, and rabbit antiserum against SPM-2 completely neutralized the T-cell-stimulating activities of CAP, suggesting that SPM-2 and CAP belong to a family of streptococcal mitogenic proteins. The SPM-2 activity with stimulation of V beta 8+ T cells was detected extensively in the culture fluids of group A streptococci, but not in those of other streptococcal species, including groups B and D streptococci, and most of the activities detected were completely inhibited by anti-SPM-2 serum. These results indicate that SPM-2 may be a newly discovered superantigen molecule, which can be commonly synthesized by group A streptococci.
authors.affiliation: Department of Microbiology, Tohoku University School of Dentistry, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Rikiishi
authors.forename: S
authors.initials: S
authors.lastname: Okamoto
authors.forename: S
authors.initials: S
authors.lastname: Sugawara
authors.forename: K
authors.initials: K
authors.lastname: Tamura
authors.forename: Z X
authors.initials: ZX
authors.lastname: Liu
authors.forename: K
authors.initials: K
authors.lastname: Kumagai
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002478:Cells, Cultured; D002848:Chromatography, DEAE-Cellulose; D006684:HLA-DR Antigens / Q000276:immunology; D006801:Humans; D007525:Isoelectric Focusing; D008213:Lymphocyte Activation; D008934:Mitogens / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D011506:Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis; D013297:Streptococcus pyogenes / Q000276:immunology*; D018089:Superantigens / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D001426:Bacterial Proteins; D006684:HLA-DR Antigens; D008934:Mitogens; D011506:Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; C108275:Streptococcus pyogenes mitogen-2; D018089:Superantigens