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Superantigenicity of helper T‐cell mitogen (SPM‐2) isolated from culture supernatants of Streptococcus pyogenes
Author(s) -
RIKIISHI H.,
OKAMOTO S.,
SUGAWARA S.,
TAMURA K.,
LIU ZX.,
KUMAGAI K.
Publication year - 1997
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1046/j.1365-2567.1997.00277.x
Subject(s) - streptococcus pyogenes , superantigen , microbiology and biotechnology , biology , t cell receptor , t cell , antigen , major histocompatibility complex , epitope , monoclonal antibody , antibody , immune system , immunology , bacteria , genetics , staphylococcus aureus
A superantigen ( Streptococcus pyogenes mitogen‐2; SPM‐2) that stimulates human helper T cells bearing unique types of variable domains of T‐cell receptor β ‐chain (TCR V β ) 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 (pI) of 6·0. This new superantigen was found to activate preferentially V β 4 + , 7 + , and 8 + T cells, whereas recombinant streptococcal pyrogenic exotoxin A and C activated V β 12 + and V β 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 β 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 β 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.