Crosslinked staphylococcal enterotoxin B stimulates CD8+ T cells only in the presence of unlinked costimulator signals.
The superantigen staphylococcal enterotoxin B (SEB) binds to class II MHC expressing cells and subsequently causes selective activation of T cells carrying appropriate T cell receptor (TCR) V beta chains. Apparently SEB acts as a bifunctional molecule by bridging class II MHC structures with the appropriate TCR-V beta chains. This assumption predicts that immobilized SEB ought to stimulate purified, class II MHC negative murine T cells. We show here that immobilized SEB lacks the ability to trigger murine CD8 T cells. Responsiveness obtained at a high T cell concentration is due to contaminating class II MHC-positive lymphocytes. Complementation of the culture system with syngeneic irradiated B cells blasts effectively restores responsiveness. The proliferating cells exhibit SEB specific cytotoxicity and a bias for V beta 8 expression. Since no evidence for leakiness of SEB covalently bound to sephadex beads was obtained, the data imply that immobilized SEB in fact binds to the TCR of T cells expressing the appropriate V beta chains. However, for primary activation additional costimulatory signals are required which can be provided in an unlinked fashion by activated B cells. Resting B cells are activated by immobilized SEB to cells expressing high costimulator activity. As such, the data point out a third function of SEB.
Miethke
T
T
Institute of Medical Microbiology and Hygiene, Technical University of Munich, Germany.
Heeg
K
K
Wahl
C
C
Wagner
H
H
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens; D003432:Cross-Linking Reagents; D004768:Enterotoxins / Q000276:immunology*; D000949:Histocompatibility Antigens Class II; D008213:Lymphocyte Activation; D051379:Mice; D008808:Mice, Inbred CBA; D013211:Staphylococcus aureus; D013601:T-Lymphocytes / Q000276:immunology*
D016827:CD8 Antigens; D003432:Cross-Linking Reagents; D004768:Enterotoxins; D000949:Histocompatibility Antigens Class II; C031818:enterotoxin B, staphylococcal