41181 (Lecture 7) Antigen Processing Presentation Audio V1
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IMUNOLOGY 41181
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Antigen Processing and Presentation
(a) Antigen with APC fixation
(b) Antigen Fixation with T Helper (TH) cell
(c) Antigen peptides with TH cell
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Antigen Processing
Definition: The method of preparing antigen material for presentation to T cells.
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Experimental Evidence 1 (a)
T-Cell Activation
Key Findings:
Efficacy of chemical fixation, utilizing Paraformaldehyde and Glutaraldehyde for APC fixation.
Fixation limits phagocytosis ability in APC.
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Experimental Evidence 2 (b)
T-Cell Activation
Key Findings:
Phagocytosis can occur before fixation, enabling antigen interaction.
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Experimental Evidence 3 (c)
T-Cell Activation
Focus on Post-Fixation
Confirmation of APC interaction but no phagocytosis post-fixation.
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Experimental Evidence 4
APC fixed with glutaraldehyde.
Fixed APC incubated with various forms of ovalbumin.
No TH activation with whole ovalbumin; TH activation observed with processed ovalbumin peptides.
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Experimental Evidence 5
Target cells incubated with virus-derived peptides.
Virus-specific T cell activation occurs when target cells are exposed to virus peptides.
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Antigen Processing and Presentation
Classification of MHC complexes:
Peptide-class I MHC Complex
Peptide-class II MHC Complex
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Antigen Presenting Cells (APCs)
Express MHC I or both MHC I and II.
Role of Target Cells: MHC I + peptide presented to CD8+ TC cells.
Role of APCs: MHC II + peptide presented to CD4+ TH cells.
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Professional APCs
Dendritic cells: Most effective, express MHC II constitutively.
Macrophages: Activated via phagocytosis to express MHC II.
B cells: Constitutive expression of MHC II.
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Types of APCs
Professional APCs: Dendritic cells, Macrophages, B cells.
Nonprofessional APCs: Fibroblasts, Thymic epithelial cells, Glial cells, etc.
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MHC Restriction (Limitation)
Importance of MHC compatibility in CTL targeting.
H-2 compatibility levels among target cells.
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MHC Restriction Class Specificity
Specificity of TCR in recognizing MHC class I and II during antigen interaction.
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Experimental Evidence
Observations of antigen strain responses and lymph node cell interactions.
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MHC II Compatibility
Activation based on the presence of histocompatible macrophages and T cells.
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Peritoneal Exudate Cells
Composition and role in response: Macrophages and T cells; adherence interactions.
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Results from MHC Compatibility Studies
Observations on activation of T cells with respective macrophage strains.
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MHC II Restriction Results
Recognition of MHC II by CD4+ TH cells in APC interactions.
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MHC Restriction MHC I Specificity
TC cell activation through interaction with MHC I producing target cells.
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H-2K MHC Histocompatibility
The role of H-2K during immune responses and target cell interactions.
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MHC Compatibility Results
Effectiveness of activated TC cells in lysing LCM-infected target cells based on MHC compatibility.
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MHC I Restriction Results
Overview of CD8+ TC cell specificity towards MHC I expressing target cells.
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T Cell Immune Response Overview
Understanding antigen specificity through TCR interactions.
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MHC Histocompatibility
Comparison between self and non-self MHC responses.
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T Cell MHC Specificity
TH/CD4 specific for MHC II; TC/CD8 specific for MHC I.
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Antigen Processing/Presentation Pathways Overview
Endogenous Pathway (MHC I) vs Exogenous Pathway (MHC II)
Key differences in processing endogenous vs exogenous antigens.
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Endogenous Pathway
Detailed steps of peptide processing in MHC I pathway in target cells.
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Endogenous Pathway
Continuous focus on the importance of peptide class I MHC complex presentation.
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Endogenous Pathway
Role of the proteasome in protein degradation and peptide generation.
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Endogenous Pathway
Description of proteasomal activity in antigen presentation.
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HLA Haplotype
Overview of Human HLA complexes critical for immune response.
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Endogenous Pathway
Focus on generation of MHC I-specific peptides through proteolysis.
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TAP Functionality
Importance of TAP in transporting peptides into the ER for MHC I binding.
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TAP Proteins
Overview of the characteristics of TAP proteins related to antigen processing.
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HLA Haplotype Loci
Structural dynamics of Human HLA complex loci.
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MHC I Complex Assembly in ER
Detailed outline of MHC I complex formation in the ER.
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Peptide-MHC I Complex Assembly in ER
Chaperone assistance in polypeptide folding and proper structure.
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MHC I-Peptide Complex Assembly Process
Overview of the process leading to the expression of the MHC I-peptide complex on the cell surface.
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Endogenous Pathway Process
Importance of peptide degradation by exopeptidases in amino acid recycling.
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Cytoplasmic Peptide Processing
Interaction of cytosolic proteins and MHC complex setup.
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Exogenous Pathway Overview
Processing of endocytosed antigens for presentation by MHC II.
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Exogenous Pathway
Emphasis on the processing mechanisms of exogenous antigens in APCs.
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Exogenous Pathway Mechanism
Role of specific receptors in antigen endocytosis.
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Ig Activity
Overview of immunoglobulin activity in opsonization and phagocytosis.
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Exogenous Pathway Vesicle Dynamics
pH changes in compartments during antigen processing.
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Exogenous Pathway Steps
Critical sequence of events from early endosome through lysosome leading to peptide binding.
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MHC II-Peptide Complex
Dynamics of invariant chain interactions and peptide loading mechanisms.
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MHC II Formation Process
Outline of how MHC II peptide complexes prevent non-specific binding.
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HLA Haplotype Loci
Recapping human HLA complex organization.
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Exogenous Pathway Overview
The role of invariant chain and HLA-DM in MHC II peptide complex formation.
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Exogenous Pathway
Overview of complex rerouting after endocytosis of antigen.
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Processing Presentation Pathways Summary
A brief comparison of both endogenous and exogenous antigen processing pathways.
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Antigen Processing Overview
Final outline of antigen processing by APCs.