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Immunology Chapter 7 Kuby
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Immunology Chapter 7 Kuby
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Immunology Chapter 7 Kuby- ANS-o In MHC I, the molecules are blocked at both ends of the groove.
§ As a result they bind shorter peptides than MHC II.
o In MHC II, the molecules are open at both ends of the groove.
- ANS-The antigenic peptides from proteasome cleavage and those from endocytic
compartments associate with MHC class I or II molecules, respectively, and the
MHC-peptide complexes are then transported to the cell membrane.
· A variety of cells can function as bona fide APCs. - ANS-o Their distinguishing feature
is their ability to express MHC class II molecules and to deliver a costimulatory, or
second activating signal, to T cells.
Three cell types are known to have these characteristics and are thus often referred to
as professional antigen-presenting cells (pAPCs): dendritic cells, macrophages, and B
lymphocytes.
· MHC class I and II molecules come in many allelic forms and exhibit semipromiscuous
peptide binding, allowing them to form stable, noncovalent interactions with a range of
different peptide ligands. - ANS-
· MHC II Peptide interaction - ANS-o Binds peptides from intracellular sources and
presents them to CD8+ cells
o Peptides bound to MHC class II molecules maintain a roughly constant elevation on
the floor of the binding groove
o The open ends and less conserved nature of the class II binding groove, allow for
greater variability in the sequence and length of class II-bound peptides
o Usually derived from exogenous extracellular processed antigens
o Exhibit anchor amino acid residues that lock them into groove
o Extends amino acid residues from groove to interact with TCRs
, ·Describe the binding pocket of MHC class I - ANS-The MHC class I binding pocket is
smaller than MHC II, more closed at the ends, and shows some amino acid anchor
residue preferences in bound peptides, while the class II pocket can accommodate
longer peptides and shows less restricted amino acid sequence preferences.
• Congenic - ANS-- genetically identical except at a single genetic region (Such as
Thy1.1 vs Thy1.2)
• Syngeneic - ANS-- identical at all genetic loci ( such as B-haplotype and D-haplotype)
Anchor residue - ANS-amino acid residues in MHC-binding peptides that interact with
pockets in the peptide-binding groove of the MHC molecule. Peptides that bind to a
given MHC allotype have the same or similar anchor residues.
Antigen-presenting cells (APCs) - ANS-o antigen-presenting cells (APCs) display
peptides associated with MHC class II molecules to CD4 T cells, and these cells are
primarily specific types of leukocytes.
§ APCs are specialized for their ability to alert the immune system to the presence of an
invader and can induce the activation of T-cell responses.
· APCs thus play a policing role in the body, with unique authorization to activate an
immune response to extracellular infection.
B cells - ANS-§ constitutively express MHC class II molecules, although at low levels,
and possess antigen-specific surface receptors. This makes them particularly efficient at
capturing and presenting their cognate antigen, or the specific epitope recognized by
their BCR.
Class I and II Molecules Exhibit Polymorphism in the Region That Binds to Peptides -
ANS-· These molecules are not as specific as antigen-specific receptors we see on
antibodies, instead they can bind to several different peptides—promiscuity
· In both types of MHC molecules, the peptide ligands are held in a largely extended
conformation that runs the length of the groove.
Class I MHC-peptide interactions - ANS-• Present peptides to CD8 + T cells
• Peptides derived from endogenous intracellular proteins
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