Binding of staphylococcal enterotoxin A to purified murine MHC class II molecules in supported lipid bilayers.
The staphylococcal enterotoxins are a family of bacterial toxins that are thought to exert their pathogenic effects by the massive activation of T lymphocytes to produce lymphokines. Activation of T cells by these toxins is dependent on MHC class II+ APC. Recent studies from a number of laboratories have implicated MHC class II proteins as the APC surface receptor for a number of the staphylococcal enterotoxins. The present report shows that staphylococcal enterotoxin A, (SEA) binds to the purified murine MHC class II molecule I-Ed reconstituted in supported planar membranes, indicating that no other cell surface proteins are required for SEA binding. The Kd for SEA binding to I-Ed was determined to be 3.5 +/- 1.6 x 10(-6) M. Specific binding of SEA to I-Ad was also observed, but the interaction was of significantly lower affinity. Binding of SEA to purified I-Ed was blocked by antibodies against both the alpha- and the beta-chain of the I-Ed molecule, but not by antibodies specific for an unrelated MHC class II protein. Binding of SEA to I-Ad was blocked by an A beta d but not by an A alpha d-specific antibody. Planar membranes containing only lipid and purified I-Ed molecules were sufficient for activation of a V beta 1 expressing T hybrid by SEA. The T cells responded to as few as 180 toxin molecules per T cell.
Lee
J M
JM
Department of Immunology, University of Toronto, Ontario, Canada.
Watts
T H
TH
D000818:Animals; D000906:Antibodies / Q000276:immunology; D004768:Enterotoxins / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D011487:Protein Conformation; D013211:Staphylococcus aureus; D013601:T-Lymphocytes / Q000276:immunology
D000906:Antibodies; D004768:Enterotoxins; D000949:Histocompatibility Antigens Class II; D008051:Lipid Bilayers; C026066:enterotoxin A, Staphylococcal