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The T-cell accessory molecule CD4 recognizes a monomorphic determinant on isolated Ia
1Department of Microbiology, University of Colorado Health Sciences Center, Denver 80262.
Summary
The CD4 protein on T cells enhances their interaction with antigen-presenting cells. This study shows CD4 binding to MHC class II molecules significantly boosts T cell responses to antigen.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- The CD4 protein is typically found on T cells that recognize antigens presented by MHC class II molecules.
- It is hypothesized that CD4 interacts with a conserved region of MHC class II, either enhancing T cell-APC interactions or delivering inhibitory signals.
Purpose of the Study:
- To investigate the functional role of CD4 in T cell activation.
- To determine if CD4 interacts with MHC class II molecules and influences T cell responses.
Main Methods:
- Utilized a unique CD4+ T hybrid cell line restricted to MHC class I.
- Incorporated purified MHC class II proteins into a planar membrane system for T cell stimulation.
- Compared the responses of CD4+ and CD4- variants of the T hybrid to isolated MHC class I molecules.
Main Results:
- MHC class II molecules significantly enhanced the response of the CD4+ T hybrid to MHC class I.
- This enhancement was observed with CD4+ T cells but not CD4- variants.
- The presence of CD4 on T cells and various MHC class II proteins on planar membranes strongly augmented T cell responses.
Conclusions:
- CD4 binds to a monomorphic region of MHC class II molecules.
- This interaction increases the overall avidity of the T cell-antigen-presenting cell interaction, thereby augmenting T cell responses.