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Mouse CD4 binds MHC class II with extremely low affinity
1Basel Institute for Immunology, Switzerland.
Insights
Researchers quantified the interaction between CD4 and MHC class II molecules using a novel rosette assay. This study reveals an extremely low binding affinity, crucial for understanding T lymphocyte development and activation.
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- CD4 interaction with MHC class II is vital for CD4 T lymphocyte thymic development and activation.
- Quantifying this molecular interaction is essential for understanding its role in immune responses.
Purpose of the Study:
- To develop and utilize a novel assay for quantifying the CD4-MHC class II interaction.
- To determine the binding affinity between mouse CD4 and MHC class II molecules.
Main Methods:
- Development of a rosette assay using beads coupled with soluble mouse CD4.
- Studying the specific binding of CD4 to MHC class II molecules expressed on A20 B lymphoma cells.
Main Results:
- Demonstrated specific binding of CD4 to MHC class II molecules on lymphoma cells.
- Revealed an extremely low binding affinity (Ka ≤ 10^4 M⁻¹) between mouse CD4 and MHC class II.
Conclusions:
- The developed rosette assay is effective for studying CD4-MHC class II molecular interactions.
- The low affinity suggests a transient or context-dependent interaction critical for T cell function.
Abstract:
Interaction of CD4 with MHC class II molecules plays a crucial role during thymic development and activation of single-positive CD4 T lymphocytes. The quantitation of this interaction is, therefore, important for understanding the role of CD4 during these events. To this end, we have developed a rosette assay, which enabled us to study this molecular interaction. By coupling soluble mouse CD4 onto beads, we could show specific binding of CD4 to MHC class II molecules on A20 B lymphoma cells. These binding studies revealed an extremely low affinity (Ka < or = 10(4) M-1) between CD4 and MHC class II molecules in mouse.