title: Role of antigen-presenting cells in activation of human T cells by the streptococcal M protein superantigen: requirement for secreted and membrane-associated costimulatory factors.
abstract: The requirements for T-cell activation by the streptococcal superantigen (SAg), pepsin-extracted M protein from type 5 streptococci (pep M5), were studied by monitoring Ca2+ influx and cell proliferation. Cells from a pep M5-specific T-cell line showed no change in intracellular Ca2+ levels in response to pep M5 when added alone or with freshly isolated autologous antigen-presenting cells (APC). However, after being incubated with pep M5 overnight, the APC secreted soluble factors that together with pep M5 induced a marked increase in intracellular Ca2+ levels in pep M5-specific T cells or freshly isolated, purified T cells. Removal of the SAg from the overnight APC-derived supernatants resulted in loss of the Ca(2+)-mobilizing activity, which was restored within seconds of addition of SAg, suggesting that both the SAg and the soluble factors synergize to induce the Ca2+ influx. Induction of cell proliferation required additional signals inasmuch as the activated APC-derived supernatant failed to synergize with pep M5 to induce the proliferation of purified T cells and required the presence of phorbol myristate acetate for this activity. Metabolically inactive, fixed APC were impaired in their ability to present pep M5 to T cells. Presentation of pep M5 by fixed APC was, however, restored when the APC-derived soluble costimulatory factors were added to the culture. Our data suggest that pep M5-induced activation of T cells is dependent on APC-derived soluble factors and an APC membrane-associated costimulatory molecule(s). These interactions may be important in regulating the in vivo responses to M proteins, could contribute to the severity or progression of infections with Streptococcus pyogenes, and may influence the susceptibility of individuals to its associated nonsuppurative autoimmune sequelae.
authors.affiliation: Veterans Administration Medical Center, Memphis, Tennessee.
authors.forename: G
authors.initials: G
authors.lastname: Majumdar
authors.forename: H
authors.initials: H
authors.lastname: Ohnishi
authors.forename: M A
authors.initials: MA
authors.lastname: Tomai
authors.forename: A M
authors.initials: AM
authors.lastname: Geller
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.forename: M E
authors.initials: ME
authors.lastname: Dockter
authors.forename: M
authors.initials: M
authors.lastname: Kotb
mesh_terms: D000938:Antigen-Presenting Cells / Q000502:physiology*; D000942:Antigens, Bacterial / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D001427:Bacterial Toxins; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins; D002478:Cells, Cultured; D004768:Enterotoxins / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000502:physiology; D006801:Humans; D008213:Lymphocyte Activation; D018089:Superantigens; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002352:Carrier Proteins; D004768:Enterotoxins; D000949:Histocompatibility Antigens Class II; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal; C014689:streptococcal M protein; C031818:enterotoxin B, staphylococcal; D002118:Calcium