1. True/False: The invariant chain protein, Ii, has only one function in MHC cla
ID: 204075 • Letter: 1
Question
1. True/False: The invariant chain protein, Ii, has only one function in MHC class II antigen presentation. This function entails Ii protein occupying the peptide-binding site of each newly synthesized class II protein, thereby preventing nascent MHC class II proteins from binding peptides or misfolded proteins in the endoplasmic reticulum.
2. Peptide editing is an important component of antigen presentation for both MHC class I and MHC class II pathways, as it drives the preferential presentation of high-affinity binding peptides. For MHC class II peptide editing, HLA-DM plays a key role. In the absence of HLA-DM:
A. MHC class II molecules traffic to the cell surface with CLIP in their binding sites.
B. No MHC class II molecules are released to traffic to the cell surface.
C. MHC class II molecules bind to HLA-DO and are inhibited from binding peptides.
D. Pathogens can evade the immune system by blocking peptide exchange on MHC class II.
E. HLA-DO competes for high-affinity binding peptides with MHC class II molecules and blocks antigen presentation.
3. True/False: The genes encoding MHC proteins are closely linked with genes encoding proteins involved in antigen processing and presentation. This genetic linkage facilitates the coordinate regulation of these genes by interferons.
Explanation / Answer
1. True.
The invariant chain protein, Ii, has only one function in MHC class II antigen presentation. This function entails Ii protein occupying the peptide-binding site of each newly synthesized class II protein, thereby preventing nascent MHC class II proteins from binding peptides or misfolded proteins in the endoplasmic reticulum.
2. (A) A. MHC class II molecules traffic to the cell surface with CLIP in their binding sites.
3. True.
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