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Staphylococcal enterotoxin H displays unique MHC class II-binding properties.
H Nilsson1, P Björk, M Dohlsten
1Active Biotech Research AB, Department of Cell and Molecular Biology, Section for Tumor Immunology, Lund University, Sweden. helen.nilsson@activebiotech.com
Journal of Immunology (Baltimore, Md. : 1950)
|December 10, 1999
Summary
Staphylococcal enterotoxin H (SEH) is a potent T cell activator with exceptionally high affinity for MHC class II molecules. Its unique binding properties allow effective presentation on antigen-presenting cells.
Area of Science:
- Immunology
- Microbial Pathogenesis
- Molecular Biology
Background:
- Staphylococcal enterotoxin H (SEH) is known as a superantigen.
- Previous studies characterized its in vivo activity.
Purpose of the Study:
- To investigate the T cell mitogenic and cytotoxic properties of SEH.
- To elucidate the unique MHC class II-binding characteristics of SEH.
Main Methods:
- Measured SEH affinity for MHC class II on Raji cells.
- Utilized competition assays with other staphylococcal enterotoxins (SEA, SEAF47A).
- Investigated zinc dependency and binding to mutated MHC class II molecules (betaH81A).
- Performed alanine substitution mutagenesis on SEH residues (D167, D203, D208).
Main Results:
- SEH exhibits the highest affinity (approx. 0.5 nM) for MHC class II among staphylococcal enterotoxins.
- SEH binding overlaps with SEA/SEAF47A at the MHC class II beta-chain.
- SEH binding is zinc-dependent but distinct from SEA's interaction with betaH81A.
- Mutagenesis of SEH residues D167, D203, D208 reduced MHC class II affinity and potency.
Conclusions:
- SEH possesses unique MHC class II-binding properties with a distinct topology compared to SEA.
- These properties enable SEH to overcome MHC class II variability and polymorphism.
- SEH facilitates effective presentation on antigen-presenting cells, even with low MHC class II expression.