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Updated: Aug 8, 2026
Visualizing Antigen Specific CD4+ T Cells using MHC Class II Tetramers
Published on: March 6, 2009
CD4/major histocompatibility complex class II interaction analyzed with CD4- and lymphocyte activation gene-3
B Huard1, P Prigent, M Tournier
1Laboratoire d'Immunologie Cellulaire, INSERM U333, Institut Gustave-Roussy, Villejuif, France.
Insights
Lymphocyte activation gene (LAG)-3Ig fusion protein blocks CD4/MHC class II interactions in cell adhesion but not cytotoxicity assays. Co-engagement of T cell receptor (TCR) with CD4 may alter this interaction, rendering it insensitive to LAG-3Ig.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- The interaction between CD4 and major histocompatibility complex (MHC) class II molecules is crucial for T cell activation.
- Lymphocyte activation gene (LAG)-3 is an inhibitory receptor expressed on activated T cells.
- Recombinant fusion proteins like CD4Ig and LAG-3Ig can be used to study molecular interactions.
Purpose of the Study:
- To investigate the binding characteristics of CD4Ig and LAG-3Ig to MHC class II molecules.
- To determine if LAG-3Ig can inhibit CD4/MHC class II interactions in different cellular contexts.
Main Methods:
- Binding assays using recombinant CD4Ig and LAG-3Ig fusion proteins.
- Cellular adhesion assays to measure CD4/MHC class II-dependent adhesion.
- T cell cytotoxicity assays to assess the impact on cell killing.
Main Results:
- CD4Ig exhibited weak, specific binding to MHC class II molecules at micromolar concentrations.
- LAG-3Ig demonstrated intermediate avidity binding to MHC class II (Kd = 60 nM at 37°C).
- LAG-3Ig inhibited CD4/MHC class II-dependent cellular adhesion but not T cell cytotoxicity.
Conclusions:
- LAG-3Ig can effectively block CD4/MHC class II interactions in specific cellular assays.
- Co-engagement of the T cell receptor (TCR) with CD4 may modulate the CD4/MHC class II interaction, making it resistant to LAG-3Ig inhibition.
Abstract:
We analyzed CD4 major histocompatibility complex (MHC) class II interactions with CD4 and lymphocyte activation gene (LAG)-3 recombinant fusion proteins termed CD4Ig and LAG-3Ig. CD4Ig bound MHC class II molecules expressed on the cell surface only when used in the micromolar range. This weak CD4Ig binding was specific, since it was inhibited by anti-CD4 and anti-MHC class II mAb. LAG-3Ig bound MHC class II molecules with intermediate avidity (Kd = 60 nM at 37 degrees C). Using LAG-3Ig as a competitor in a CD4/MHC class II-dependent cellular adhesion assay, we showed that this recombinant molecule was able to block CD4/MHC class II interaction. In contrast, no inhibition was observed in a CD4/MHC class II-dependent T cell cytotoxicity assay. Together, these results suggest that co-engagement of the TcR with CD4 alters the CD4/MHC class II molecular interaction to become insensitive to LAG-3Ig competition.
