6.4 Fill-in-the-Blanks: Cell membrane-destined polypeptides are translocated to the lumen of the endoplasmic reticulum, which is intriguing because the MHC class I presented peptides are found in the ________. Further research revealed that presentation of cytosolic peptides is possible due to a family of ABC transporters, ______, that mediate the ATP-dependent transport of peptides into the lumen of the _______. This transporter complex has limited specificities for the transported peptides; for example, peptides are generally ________ amino acids in length and transport is biased in favor of ________ residues in the 6.9 Multiple Choice: Defective function of which of the carboxy terminus and against _________ residues within the first _______ amino-terminal residues.
6.5 Multiple Choice: CD8 dendritic cells are uniquely capable of strongly cross-presenting antigens. Which of the following options correctly matches a transcription factor essential for CD8 dendritic cell development and a surface marker uniquely expressed by these cells?
A. CIITA, CD74 B. BATF3, CD4 C. CIITA, CD94 D. BATF3, XCR1 6.6 Matching: Match the following terms with the appropriate description:
A. TRiC i. Retains the MHC class I molecule α chain in a partly folded state
B. ERAAP ii.  Protects peptides produced in the  cytosol from complete degradation
C. Calnexin iii. Forms a bridge between the MHC  class I molecule and the TAP complex
D. ERp57 iv. Trims the amino terminus of peptides that are too long for MHC binding
E. Tapasin v.  Breaks and re-forms disulfide bonds in the MHC class I α domain during peptide loading 6.7 True or False: Cytosolic antigens are not presented through MHC class II molecules.
6.8 Matching: Order the following events in the sequence in which MHC class II processing happens in an antigen-presenting cell: ____The CD74 trimerization domain is cleaved.
____MHC class II is translocated into the endoplasmic reticulum.
____Cathepsin S cleaves LIP22 and leaves the CLIP fragment on the MHC molecule.
____CD74 trimers bind non-covalently to MHC class II α:β heterodimers.
____HLA-DM catalyzes the release of CLIP and promotes peptide editing. ____MHC class II heterodimers are released from calnexin for transport to a low-pH endosomal compartment.
General references.
Germain, R.N.: MHC-dependent antigen processing and peptide presentation: providing ligands for T lymphocyte activation. Cell 1994, 76:287–299.
Klein, J.: Natural History of the Major Histocompatibility Complex. New York: Wiley, 1986.
Moller, G. (ed.): Origin of major histocompatibility complex diversity. Immunol. Rev. 1995, 143:5–292.
Trombetta, E.S., and Mellman, I.: Cell biology of antigen processing in vitro and in vivo. Annu. Rev. Immunol. 2005, 23:975–1028.
following proteins will result in failed CD8 T-cell priming?
A. HLA-DM
B. Cathepsin S C. TAP1/2 D. CD74 6.10 Multiple Choice: Defective function of which of the following proteins will result in decreased cytosolic peptide presentation on MHC class II?
A. IRGM3 B. BATF3 C. MARCH-1 D. TAP1/2 6.11 True or False: Superantigens do not induce an adaptive immune response and are independent of peptide-specific MHC–TCR interactions.
6.12 Multiple Choice: Which of the following statements is false?