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Assembly, transport, and function of MHC class II molecules
1Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510.
Annual Review of Immunology
|January 1, 1994
Summary
MHC class II molecules bind peptides within endosomes after invariant chain degradation. These peptide-loaded complexes are then presented to CD4+ T cells on the cell surface.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- MHC class II molecules are crucial for adaptive immunity.
- Their assembly and peptide loading occur through a complex cellular pathway.
Purpose of the Study:
- To elucidate the trafficking and peptide-loading mechanisms of MHC class II molecules.
- To understand the role of the invariant chain in this process.
Main Methods:
- The study reviews existing evidence on MHC class II assembly, trafficking, and peptide binding.
- It discusses findings related to chaperone-mediated assembly, endosomal targeting, and invariant chain degradation.
Main Results:
- MHC class II-invariant chain complexes assemble in the ER and traffic through the Golgi to endosomes.
- Invariant chain degradation in late endosomes/pre-lysosomes releases alpha beta dimers for peptide binding.
- Peptide generation, potentially in lysosomes, and MHC-encoded factors are involved in complex formation.
Conclusions:
- The invariant chain guides MHC class II to endosomes for peptide loading.
- The precise mechanisms of MHC class II-peptide complex formation and cell surface transport remain areas for further investigation.
- MHC class II molecules present antigenic peptides to CD4+ T cells, a critical step in immune response.