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Differential requirements for CD4 in TCR-ligand interactions
1Center for Immunology, Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|October 21, 1999
Summary
The coreceptor CD4 (cluster of differentiation 4) is crucial for T cell activation. Its absence significantly impairs recognition of altered peptide ligands (APLs), impacting T cell signaling and immunological synapse formation.
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- CD4 (cluster of differentiation 4) is a critical coreceptor in T cell activation.
- It mediates both extracellular antigen recognition and intracellular signaling pathways.
- Understanding CD4's role is vital for dissecting T cell responses.
Purpose of the Study:
- To investigate the functional significance of CD4 in T cell recognition of agonist and altered peptide ligands (APLs).
- To elucidate the specific domains and interactions of CD4 essential for T cell activation by different ligand types.
Main Methods:
- Generation of CD4-deficient T cell lines expressing specific T cell receptors (TCRs).
- Utilized CD4 variants with mutations in p56lck association or MHC class II binding domains.
- Assessed T cell responsiveness to agonist peptides and APLs.
Main Results:
- Loss of CD4 expression significantly reduced T cell recognition of APLs, with varied effects on agonist peptide response.
- Restoration of p56lck association partially restored APL stimulation, while MHC class II interaction was essential for full ligand reactivity.
- CD4 was not required for APL-mediated antagonism.
Conclusions:
- CD4 is integral to the initial formation of the immunological synapse.
- The functional requirements for CD4 in T cell activation differ based on ligand potency.
- These findings highlight the multifaceted role of CD4 in adaptive immunity.