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Class I MHC alpha 3 domain can function as an independent structural unit to bind CD8 alpha
J Fayen1, J H Huang, H Meyerson
1Institute of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.
Molecular Immunology
|March 1, 1995
Summary
This study reveals that CD8 alpha directly binds to the alpha 3 domain of class I MHC molecules. This interaction is specific and does not require other cellular components for T cell recognition.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- Cytotoxic T cell function relies on CD8-mediated interactions with target cells.
- CD8 interacts with a specific region on the alpha 3 domain of class I MHC molecules.
Purpose of the Study:
- To develop a cell-free assay to directly measure the molecular interaction between CD8 and class I MHC.
- To characterize the binding kinetics and specificity of this interaction.
Main Methods:
- A cell-free system using soluble CD8 alpha and a plate-bound HLA-A2.1 alpha 3/MalE fusion protein.
- Measurement of binding affinity (Kd) and inhibition studies using monoclonal antibodies.
Main Results:
- Demonstrated specific and saturable binding between soluble CD8 alpha and the alpha 3 domain.
- Determined the dissociation constant (Kd) for this interaction to be 4.5 x 10(-7) M.
- Monoclonal antibodies targeting CD8 or the alpha 3 domain inhibited binding, while others did not.
Conclusions:
- The interaction between CD8 alpha and the class I MHC alpha 3 domain is direct and specific.
- This interaction does not necessitate neighboring class I MHC sequences or beta 2-microglobulin.