Card Set Information

2010-03-31 17:13:39
2 2_Immune_MHCs

MHCs and antigen presentation
Show Answers:

  1. Q: What is MHC?
    A: major histocompatiability complex
  2. Q: What is a syngeneic graft?
    A: graft b/w genetically identical animals
  3. Q: What is the human equivalent to a syngeneic graft?
    A: autologous graft
  4. Q: What is an allogeneic graft?
    A: graft b/w individuals with dissimilar genetics
  5. Q: How do human transplants (allogeneic) work?
    A: the immune response must be suppressed
  6. Q: What is a graft vs. host disease?
    A: the graft attacks the host, usually marrow
  7. Q: What are the 2 classes of genes involved in graft rejection?
    A: MHC Class I and MHC Class II
  8. Q: What are MHC Class I proteins in humans?
    A: HLA antigens ( human leukocyte antigens)
  9. Q: What are MHC Class II proteins in humans?
    A: DR, DQ, DP
  10. Q: Where are the MHC gene products found?
    A: On cell surfaces
  11. Q: Are MHC gene products secreted?
    A: No, they are cell surface receptors
  12. Q: What are the MHC Class I gene products (3)?
    A: HLA-A, HLA-B, HLA-C
  13. Q: What is beta2 microglobulin
    A: A protein that forms a heterodimer with class I protein
  14. Q: How many different Class I chains do humans have on each cell?
    A: 6, due to co-dominant expression, A=B=C
  15. Q: List the MHC Class I protein domains (5)
    A: Extracellular (3), alpha 1, 2 & 3, transmembrane, cytoplasmic
  16. Q: What domains houses the cleft?
    A: the extracellular domains
  17. Q: How long is the peptide that fits in the Class I cleft?
    A: approximately 9 amino acids
  18. Q: What domains are polymorphic on MHC I?
    A: alpha 1 and alpha 2
  19. Q: Why is the alpha 3 domain constant, on MHC I?
    A: so beta2 microglobulin can attach, as well as CD8 binding
  20. Q: Can we ever see the MHC I cleft empty?
    A: No, either self, virus or degraded
  21. Q: What domain is polymorphic on MHC II?
    A: alpha 1 and beta 1
  22. Q: What domains are constant on MHC II?
    A: alpha 2 and beta 2
  23. Q: Where do the peptides for a Class I protein come from?
    A: self or viral proteins synthesized in the cell
  24. Q: Class II proteins present peptides from?
    A: extracellular entities
  25. Q: Enzymes that create peptides presented on the MHC II are?
    A: endosomal/lysosomal proteases
  26. Q: Enzymes that create peptides presented on MHC I are?
    A: cytosolic proteasomes
  27. Q: What is the site of peptide loading in the MHC II?
    A: specialized vesicular compartments
  28. Q: What is the site of peptide loading in the MHC I?
    A: endoplasmic reticulum (ER)
  29. Q: What is TAP?
    A: tranporter associated with antigen presentation, class I
  30. Q: Which way does TAP transport peptides?
    A: cytosol to inside the ER, backwards
  31. Q: What happens if an MHC doesn't have a peptide in the cleft?
    A: it is degraded
  32. Q: Where does CD4 bind to MHC II?
    A: beta 2 domain
  33. Q: What is a CLIP?
    A: self peptide that is removed from MHC II so it can bind foreign peptides
  34. Q: What are TAP 1 & 2?
    A: peptide transporters in the ER, for MHC I
  35. Q: What is co-dominant expression?
    A: both parental alleles of each MHC gene are expressed
  36. Q: What does co-dominant expression do?
    A: increase the number of different MHC molecules that can present peptides to T cells
  37. Q: What does antigen presentation refer to?
    A: Peptides presented within MHC class I/II clefts to the T-cell receptor (TCR).
  38. Q: For T cell recognition of a foreign element, T cell will only recognize:
    A: Peptides, linear sequences and the peptide in context.
  39. Q: What is MHC restriction?
    A:Specific T cells recognize foreign peptide sequences within the cleft of a self MHC molecule.
  40. Q: Can MY T cells recognize a peptide in the cleft of YOUR class I/II proteins?
    A: No, unless we have identical class I/II proteins.
  41. Q: How has the immune system solved the problem of killing both extracellular and intracellular pathogens?
    A: It kills infected cells with cytotoxic T cells, and produces antibodies to neutralize extracellular pathogens.
  42. Q: What kind of cells have MHC class II molecules?
    A: Antigen presneting cells (Accessory cells): B cells, Macrophages, Dendritic cells.
  43. Q: How do B cells take up protein? Is this method efficient?
    A: Proteins is taken up through Ig complexes and complement receptors on the surface of the cell. This is very efficient, as Ig bind antigen with high affinity.
  44. Q: What are Langerhans cell, and where are they located?
    A: They are dendritic cells, and are located in the skin.
  45. Q: What do dendritic cells do upon the uptake of antigen?
    A: Process it and migrate from the periphery into lymph nodes for activation of T cells.
  46. Q: What organelle is responsible for digestion of antigen into peptides for the exogenous pathway?
    A: lysosome
  47. Q: Which MHC molecule has an invariant chain prior to being loaded with a peptide?
    A: MHC II
  48. Q: Where is the MHC II loaded with peptides and, are these peptides derived from endogenous or exogenous proteins?
    A: The MHC II is loaded in the vescle formed by the fusion of the lysosome with the MHC vesicle. The peptides are of exogenous origin.
  49. Q: Where is the MHC I loaded with peptides, and what organelle generates these peptides?
    A: The MHC I is loaded in the RER with peptides that have been generated from the proteasome.
  50. Q: How long do peptide expressing MHC I/II exist on the cell surface?
    A: MHC II lasts about 12 hours, MHC I has a half-life of 10-15 hours.
  51. Q: MHC II is loaded with what peptides?
    A: exogenous
  52. Q: MHC I is loaded with what peptides?
    A: endogenous
  53. Q: What is the origin of most peptides found in the MHC I in a healthy person, and in a person with a cold?
    A: self proteins, viral proteins.
  54. Q: What is the origin of most peptides found in the MHC II in a healthy person, and in a person with strep throat?
    A: self proteins, bacterial proteins.
  55. Q: What cells express class I proteins?
    A: virtually all cells.