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LICOS, a primordial costimulatory ligand?
D Brodie1, A V Collins, A Iaboni
1Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX1 3RE, UK.
Current Biology : CB
|April 4, 2000
Summary
Researchers discovered a new molecule, ligand of ICOS (LICOS), that interacts with ICOS and potentially other T cell regulators. This finding reveals a novel costimulatory pathway distinct from the classical B7-1/B7-2 interactions.
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- Mammalian T cell activation relies on costimulatory signals from B7-1 (CD80) and B7-2 (CD86) binding to CD28 and CTLA-4.
- The function of the CD28-like protein ICOS in relation to the B7 pathway was previously unclear.
Purpose of the Study:
- To investigate the molecular interactions of ICOS and determine its role in T cell costimulation.
- To identify the ligand for ICOS and elucidate its binding characteristics.
Main Methods:
- Protein binding assays at varying temperatures.
- Sequence comparisons of identified molecules with known homologs.
- Analysis of ICOS and its novel ligand interactions.
Main Results:
- ICOS binds to a novel B7-related molecule, termed ligand of ICOS (LICOS).
- LICOS exhibits specific binding to ICOS at physiological temperatures but also weakly binds CD28 and CTLA-4 at non-physiological temperatures.
- Sequence analysis suggests LICOS is evolutionarily conserved, with homologs in avian and murine species.
Conclusions:
- A novel costimulatory pathway involving ICOS and LICOS has been identified.
- LICOS represents a distinct costimulatory ligand, potentially separate from the canonical B7 pathway.
- LICOS may be the functional homolog of a primordial vertebrate costimulatory ligand.