title: Metabolically active antigen presenting cells are required for human T cell proliferation in response to the superantigen streptococcal M protein.
abstract: M protein from type 5 group A streptococci has been identified as a member of the family of polyclonal T cell activators termed superantigens because it preferentially stimulates T cells bearing specific V beta elements of the T cell receptor (TCR). In this study the molecular and cellular requirements for presentation of this protein to T cells were investigated. Only accessory cells (AC) expressing class II major histocompatibility complex (MHC) molecules were capable of supporting T cell activation in response to a 22 kDa fragment of M protein (pep M). Despite the need for class II elements, processing of pep M5 by the antigen-presenting cells (APC) was not required for T cell proliferation induced by pep M5. Fixation of APC by paraformaldehyde (PF) treatment impaired their ability to induce optimal T cell proliferation in response to pep M5 without significantly affecting interleukin (IL-2) production. In contrast, PF-fixation of cells from the B cell lymphoma line, Raji, did not affect their ability to present pep M5 to human T cells. Addition of rIL-1 and IL-6 to PF-treated APC restored pep M5-induced blastogenesis. Our data suggest that pep M5 directly associates with HLA class II molecules forming a complex that can induce IL-2 production but not optimal proliferation by T cells. Additional signals provided by the AC are required to trigger optimal T cell proliferation in response to this superantigen.
authors.affiliation: VA Medical Center, Memphis, TN 38104.
authors.forename: M A
authors.initials: MA
authors.lastname: Tomai
authors.forename: E H
authors.initials: EH
authors.lastname: Beachey
authors.forename: G
authors.initials: G
authors.lastname: Majumdar
authors.forename: M
authors.initials: M
authors.lastname: Kotb
mesh_terms: D000938:Antigen-Presenting Cells / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D002352:Carrier Proteins; D002460:Cell Line; D004768:Enterotoxins / Q000276:immunology; D005557:Formaldehyde / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis; D015850:Interleukin-6 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000276:immunology*; D011108:Polymers / Q000494:pharmacology; D013601:T-Lymphocytes
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004768:Enterotoxins; D000949:Histocompatibility Antigens Class II; D007375:Interleukin-1; D007376:Interleukin-2; D015850:Interleukin-6; D011108:Polymers; C014689:streptococcal M protein; D005557:Formaldehyde; C031818:enterotoxin B, staphylococcal; C003043:paraform