Ag Processing
Transcript of Ag Processing
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The antigen receptors on the surface of B and T cellsThe antigen receptors on the surface of B and T cells
B cells have about 100,000 molecules
of a single antibody receptor per cell,
which has specificity for one antigen
epitope.
T cells bearing the surface membraneprotein CD4 always recognize
peptides bound to MHC class II
proteins and function as Th cells.
T cells bearing the surface membraneprotein CD8 always recognize peptide
antigens bound to MHC class I
proteins and function as cytotoxic T
cells.
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Endocytosis Phagocytosis Phagocytosis Receptor-
mediatedphagocytosis
Receptor-mediated
phagocytosis
MHC
expression
Constitutive (+++) Inducible
(-)
Inducible
(++)
Constitutive (++) Constitutive
(+++)
Constitutive
(CD80/86)
Inducible
CD80/86
(-)
Inducible
(CD80/86)
(++)
Inducible
CD80/86
(-)
Inducible
(++)
T-cell
activation
Nave cells
Effector T cells
Memory T cells
-- Effector T
cells
Memory T
cells
Effector T cells
Memory T cells
Nave cells
Effector T cells
Memory T cells
Ag capture
Co-
stimulation
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Endogenous antigen processing: MHC class I peptideEndogenous antigen processing: MHC class I peptide
presentationpresentation
Intracellular proteins of host and virus are marked for
degradation by ubiquitination and are degraded by theProteasome.
The resulting viral peptides are transported into the ER
lumen by the Tap1-Tap2 heterodimeric transporter.
In the ER lumen, viral peptides associate with newly
synthesized MHC class I molecules.
MHC class I-peptide complex is transported to the cellsurface via the golgi compartments.
On the cell surface, the MHC class I-peptide complex
interacts with the T- cell receptor of a Tc cell carrying the
CD8 coreceptor.
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Endogenous antigen processing: MHC class I peptide presentationEndogenous antigen processing: MHC class I peptide presentation
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Exogenous antigen processing: MHC class II peptideExogenous antigen processing: MHC class II peptide
presentationpresentation
MHC class II complex is prevented form binding to viral
peptides in the ER by association with the invariant chain.
The complex is transported through golgi where the
invariant chain is removed, activating the MHC class II
complex.
The peptides are derived from extracellular proteins
that enter the cell by endocytosis.
Viral proteins are degraded in the lysosomes by
proteases that are activated by low pH. Endosomes fuse with vesicles containing MHC class II.
On the surface of the cell the MHC class II complex
interacts with the T cell receptor of a Th cell carrying the
CD4 coreceptor.
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Exogenous antigen processing: MHC class II peptideExogenous antigen processing: MHC class II peptide
presentationpresentation
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Dendritic cell
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Interaction between APC and lymphocyte
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INTERACTION BETWEEN APC AND T-LYMPHOCYTE
IMMUNE SYNAPSE
APC-cell
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