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Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation
Published on: February 28, 2019
Major histocompatibility complex class II invariant chain expression in non-antigen-presenting cells
H Veenstra1, W F Ferris, P J Bouic
1Department of Medical Biochemistry, University of Stellenbosch, University of Cape Town, Cape Town, South Africa.
The major histocompatibility complex (MHC) class II invariant chain (Ii) is found in T cells and NK cells, not just antigen-presenting cells. A novel associated molecule, p77, suggests a broader function for Ii beyond antigen presentation.
Area of Science:
- Immunology
- Cell Biology
Background:
- The major histocompatibility complex (MHC) class II invariant chain (Ii) is traditionally known for its role in antigen presentation.
- Its expression is generally expected in antigen-presenting cells (APCs).
Purpose of the Study:
- To investigate the intracellular expression of the MHC class II invariant chain (Ii) in non-antigen-presenting cells.
- To characterize a novel associated molecule (p77) found with Ii in T cells.
Main Methods:
- Immunoprecipitation using anti-Ii monoclonal antibodies (mAbs) VCD-1 and BU-45.
- Analysis of Ii and associated p77 molecule expression in T cells, NK cells, and APCs.
Main Results:
- The MHC class II invariant chain (Ii) is expressed intracellularly in resting peripheral blood T cells and NK cells, which are not professional APCs.
- A 77,000 molecular-weight molecule (p77) is associated with Ii in T cells, but minimally in APCs.
- The binding epitope recognized by mAb BU-45 on Ii appears hidden in the p77-Ii complex, while the VCD-1 epitope remains exposed.
Conclusions:
- The presence of the p77-Ii complex in non-professional APCs suggests a function for Ii beyond its established role in antigen presentation.
- The differential epitope accessibility indicates structural changes within the p77-Ii complex.
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