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Murine Ia-associated invariant chain's processing to complex oligosaccharide forms and its dissociation from the I-Ak
Journal of Immunology (Baltimore, Md. : 1950)
|July 1, 1985
Summary
Murine invariant chain (Ii) processing to a complex form (Ii-c) occurs slowly, taking about 120 minutes. This slow processing may trigger Ii dissociation from I-Ak complexes, facilitating Ia antigen transport.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Invariant chain (Ii) is crucial for the proper folding and transport of MHC class II molecules.
- Understanding Ii processing is key to deciphering antigen presentation pathways.
Purpose of the Study:
- To characterize the processing of murine invariant chain (Ii) in B cell lymphoma AKTB-1b.
- To determine the kinetics of Ii processing relative to its dissociation from I-Ak complexes.
Main Methods:
- Immunoprecipitation using anti-I-Ak and anti-Ii monoclonal antibodies.
- Peptide mapping with reverse-phase HPLC to identify Ii forms.
- Endo H and Endo F deglycosylation assays.
- Pulse-chase metabolic labeling and surface iodination.
Main Results:
- A novel complex oligosaccharide form of Ii (Ii-c) was identified, resistant to Endo H but sensitive to Endo F.
- Ii-c is expressed on the plasma membrane.
- Ii processing to Ii-c has a half-life of ~120 minutes, significantly slower than I-Ak alpha/beta chain processing (~15-20 minutes).
- Ii dissociates from I-Ak complexes around 100-120 minutes, with minimal Ii-c remaining associated after 300 minutes.
Conclusions:
- Ii processing to Ii-c is a slow event that may induce dissociation from I-Ak complexes.
- This dissociation is consistent with Ii's role as a carrier for Ia antigens to the cell surface.
- Late processing events, such as sialylation of Ii or I-Ak chains, could mediate Ii-I-Ak dissociation.