Immunology Quiz- Antigen Processing And Presentation

Class I MHC molecules are found on the surface of all nucleated cells. This means that every cell in the body that has a nucleus will display class I MHC molecules on its surface. On the other hand, class II MHC molecules are primarily found on antigen-presenting cells such as B cells, dendritic cells, and macrophages. These cells are specialized in capturing and presenting antigens to activate the immune response. Therefore, the correct answer is "All nucleated cells" because class I MHC is found on all cells, while class II MHC is not.

Peptide antigens generated in the cytosolic compartment, such as during intracellular infections like viruses, bind to Class I MHC molecules for presentation to CD8+ T cells. On the other hand, peptide antigens generated in vesicles, such as during extracellular infections like bacteria, bind to Class II MHC molecules for presentation to CD4+ T cells.

The proteasome plays a crucial role in the processing pathway for intracellular antigens. It breaks down viral protein molecules until peptides of 8-11 residues are formed. These peptides are then able to bind to class I MHC molecules, which is essential for the immune system to recognize and respond to the viral antigens.

The correct answer is CD4+; Class II; CD8+; Class I. This is because CD4+ T cells interact with antigen-presenting cells (APCs) through MHC Class II molecules, while CD8+ T cells interact with target cells through MHC Class I molecules. This interaction is MHC-restricted, meaning that the T cell receptor can only recognize antigens presented on MHC molecules that match its own specificity. Therefore, CD4+ T cells specifically interact with MHC Class II molecules, and CD8+ T cells specifically interact with MHC Class I molecules.

In the processing pathway for extracellular antigens, synthesis of MHC class II and invariant chain (li) occurs in the endoplasmic reticulum. The endoplasmic reticulum is responsible for protein synthesis and folding, and it is where MHC class II molecules and the invariant chain are synthesized before being transported to the Golgi apparatus for further processing and maturation. The other options, such as cytosol, ribosomes, and lysosomes, are not involved in the synthesis of MHC class II and invariant chain in the processing pathway for extracellular antigens.

The correct answer is "Reduced number of class I MHC molecules available to display peptides to CD8+ lymphocytes." This is because the protein expressed by certain strains of adenovirus inhibits the transcription of class I MHC molecules. Class I MHC molecules are responsible for presenting peptides to CD8+ lymphocytes, which are important for immune responses. Therefore, if the transcription of class I MHC molecules is inhibited, there will be a reduced number of these molecules available to display peptides to CD8+ lymphocytes.

TAP permits the peptides to traverse the membrane bilayer of the endoplasmic reticulum and bind in the empty peptide-binding groove of nascent MHC Class I molecules being synthesized in the endoplasmic reticulum.

The correct answer is "Blocks; Degraded". The invariant chain blocks the empty peptide-binding groove, preventing peptides from entering. However, after vesicle fusion, the invariant chain is degraded, allowing peptides to enter the MHC class II groove.

The consequence of the protein of herpes simplex virus (HSV) binding to TAP and inhibiting peptide transport into the endoplasmic reticulum is that fewer peptides will be available to bind to class I MHC molecules. Class I MHC molecules are responsible for presenting peptides to CD8+ lymphocytes, which are important for immune responses. Therefore, if fewer peptides are available, there will be a reduced number of class I MHC molecules available to display peptides to CD8+ lymphocytes. This can ultimately affect the immune response against HSV.

Mutations in TAP-1 or TAP-2 can affect the function of the TAP heterodimer, which is involved in antigen presentation. Antigen presentation is crucial for the activation of the immune system and the recognition of pathogens. Therefore, when TAP function is compromised, it can lead to a weakened immune response, making individuals more susceptible to infections, particularly in the upper respiratory tract. This explains why upper respiratory tract infections are common in patients with TAP mutations.