Identification of residues in the V domain of CD80 (B7-1) implicated in functional interactions with CD28 and CTLA4
C A Fargeas1, A Truneh, M Reddy
1Laboratoire d'Immunologie, Institut de Recherches Cliniques de Montréal, Québec, Canada.
Insights
Researchers identified key residues in CD80 (B7-1) crucial for binding to CD28 and CTLA4, impacting T cell costimulation and adhesion. This finding helps understand the structural basis of these critical immune interactions.
Area of Science:
- Immunology
- Molecular Biology
- Structural Biology
Background:
- CD80 (B7-1) is an immunoglobulin superfamily molecule on hematopoietic cells.
- It provides costimulatory signals to T cells via CD28 interaction.
- CD80 also binds to CTLA4 on activated T cells.
Purpose of the Study:
- To identify critical residues in human CD80 for CD28 binding.
- To investigate the role of these residues in CD28-mediated T cell adhesion and IL-2 production.
- To assess the importance of these residues for CTLA4 interaction.
Main Methods:
- Generation of human CD80 mutants.
- Assays to test CD80 mutant binding to CD28.
- Measurement of T cell adhesion and IL-2 production.
- Analysis of CD80 mutant interaction with CTLA4.
Main Results:
- Two hydrophobic residues in the V-like domain of CD80 are critical for CD28 binding.
- These residues are also important for CTLA4 interaction.
- One identified residue, Y87, is conserved across species in CD80 and CD86.
Conclusions:
- Specific hydrophobic residues in CD80 are essential for interaction with both CD28 and CTLA4.
- These findings elucidate structural requirements for CD80/CD86 binding to CD28/CTLA4.
- Understanding these interactions is key for T cell costimulation research.
Abstract:
The CD80 (B7-1) molecule is a 45-60-kD member of the immunoglobulin superfamily that is expressed on a variety of cell types of haematopoietic origin. CD80 can provide a critical costimulatory signal to T cells by interacting with the T cell surface molecule CD28. CD80 also binds to the CD28-related molecule CTLA4, which is expressed on activated T cells, Recently, additional ligands of CD28 and CTLA4 have been described in mice and humans. One of them, CD86 (B-70 or B7-2) was characterized at the molecular level. Although similar in predicted structure to CD80, it is distantly related in amino acid sequence. In this study, human CD80 mutants were generated and tested for their ability to maintain the interaction with CD28 leading to adhesion and enhanced IL-2 production. Two hydrophobic residues in the V-like domain of CD80 were identified as critical for binding to CD28 and are also important for the interaction with CTLA4. These residues are adjacent to the epitope of the BB1 antibody, which inhibits CD28-CD80 interactions. One of these residues, Y87, is conserved in all CD80 and CD86 cloned from various species. These results being to unravel the structural requirements for binding to CD28 and CTLA4.
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