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Updated: Aug 8, 2026
Identification of Mouse and Human Antibody Repertoires by Next-Generation Sequencing
Published on: March 15, 2019
CD4 and the immunoglobulin superfamily
A N Barclay1, R L Brady, S J Davis
1MRC Cellular Immunology Unit, Sir William Dunn School of Pathology, University of Oxford, U.K.
Insights
The CD4 glycoprotein, crucial for T cell recognition and HIV entry, features an extracellular region with four immunoglobulin-like domains. Structural analysis confirms these domains possess typical immunoglobulin folds, offering insights into CD4 evolution.
Area of Science:
- Immunology
- Structural Biology
- Virology
Background:
- CD4 is a cell surface glycoprotein vital for T lymphocyte recognition of foreign proteins.
- CD4 functions as the primary receptor for the human immunodeficiency virus (HIV).
- The extracellular region of CD4 exhibits sequence similarities to immunoglobulin domains.
Purpose of the Study:
- To elucidate the structural characteristics of CD4 domains 3 and 4.
- To analyze the sequence similarities within the extracellular region of CD4.
- To understand the evolutionary implications of CD4's immunoglobulin-like folds.
Main Methods:
- Monoclonal antibody-based identification of CD4.
- Amino acid sequence analysis of CD4.
- X-ray crystallography for determining the structure of CD4 domains 3 and 4.
Main Results:
- The extracellular region of CD4 comprises four distinct regions with sequence similarities to immunoglobulin domains.
- X-ray crystallography revealed that CD4 domains 3 and 4 possess typical immunoglobulin-like folds.
- These findings are consistent with the previously determined structures of CD4 domains 1 and 2.
Conclusions:
- The structural determination of CD4 domains 3 and 4 further solidifies their immunoglobulin-like nature.
- The identification of multiple immunoglobulin-like folds in CD4 provides insights into its function and evolution.
- This structural information aids in understanding CD4's role in T cell recognition and HIV interaction.
Abstract:
The CD4 membrane glycoprotein was one of the first cell surface antigens to be identified using monoclonal antibodies. It was shown to have a central role in the control of the recognition of foreign proteins by T lymphocytes and later as a receptor for the human immunodeficiency virus (HIV). The analysis of the amino acid sequence of CD4 showed that the extracellular region comprised four regions with sequence similarities to immunoglobulin domains. The structure of domains 3 and 4 of CD4 has been determined by X-ray crystallography and, like domains 1 and 2 previously determined, these have typical immunoglobulin-like folds. The results are discussed with respect to the identification of other domains with immunoglobulin-like folds from amino acid sequence data, and the evolution of CD4.
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