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26 Cards in this Set
- Front
- Back
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Where protein antigens are degraded and peptides are associated with MHC molecules in APC
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Antigen Processing
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Synthesized outside of APC and processed and presented on MHC class II molecules
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Exogenous Antigens
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Synthesized or modified within APC and are processed and presented on MHC class I molecules
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Endogenous Antigens
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How do the dendritic cells and the macrophages bring antigens in (exogenous)?
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By PRR = pattern recognition receptors
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How do the B cells bring antigens in (exogenous)?
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by Ag-Ab complex, use mIg (membrane immunoglobin)
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Where are the endogenous antigens made?
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In the APCs.
In Macrophages, endogenous proteins come from microbe that evade from phagosome |
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What is the exogenous antigen processing pathway?
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Endocytosis of extracellular microbe-->MHC meets with endocytosed vesicle-->antigen presented to CD4+
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What is the endogenous antigen processing pathway?
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Cytosolic microbe breaks endocytic vesicle-->degrades proteins-->peptide pool will go into ER-->join with class I MHC molecules-->present to CD8+ cells
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MHC II pathway
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Uptake of extracellular proteins-->endosomes fuse with lysosomes-->alpha & beta chains made in ER but not joined together, so invariant chain serves as an adhesion factor. Now APC made and is exocytosed and joins with endosome+lysosome-->CLIP on invariant chain is removed by DM and a peptide from the pool enters space. Now peptide-MHC II is presented to the CD4+
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MHC I pathway
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1. Endogenous proteins via phagocytosis or vesicle break
2. Proteosome chops down proteins 3. TAP is a protein transporter that transports peptides from the cytoplasm to ER. 4. MHC I and peptides assembled in ER. 5. Go to cell surface and MHC I-peptide complex recognized by CD8+ |
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Compare MHC structure of I and II
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MHC I: alpha, Beta 2 micro
MHC II: alpha, beta |
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Where are MHC I found vs. MHC II?
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MHC I: on all nucleated cels
MHC II: Professional APCs = DC, Macrophages, and B cells |
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What is the peptide length of MHC I vs. MHC II?
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MHC I: 8-10 aa
MHC II: 10-30 aa |
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What is the source of peptide for MHC I and MHC II?
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MHC I: exogenous, cytoplasm
MHC II: endosomal/lysosome |
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What is the processing enzyme of MHC I and MHC II?
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MHC I: proteosome
MHC II: protease |
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Where is teh assembly place for MHC I and MHC II?
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MHC I : ER
MHC II: exocytotic vesicle |
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Transporter for MHC I and MHC II?
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MHC I: TAP
MHC II: none |
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Are there any accessory parts of MHC I and MHC II?
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Yes, MHC II has an invariant chain, DM
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Cross-Presentation
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Typically, exogenous proteins are process by MHC II and presented to CD4+
Typically, endogenous proteins are processed by MHC I and presented to CD8+ Cross presentation when protein comes in exogenously but processed by MHC I pathway. |
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Cross-presentation is commonly used in what type of cells?
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Dendritic cells
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Explain the antigen presentation in cell mediated immunity of MHC II pathway.
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Clears extracellular pathogens
1. Macrophage activation 2. Stimulates T helper cells which secretes cytokines 3. Stimulates macrophages leading to destruction of microbe |
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Explain the antigen presentation in cell mediated immunity of MHC I pathway.
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Clears intracellular pathogens via clonal expansion.
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What type of antigens are recognized by B and T cells?
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B cells recognize antigens in all forms.
T cells recognize antigens displayed by MHC |
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MHC molecules are not found on red blood cells. What is the disadvantage for human if they are?
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Blood transfusions would be difficult
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Red blood cells do not express MHC molecules on their surface. NK cells recognize cells without surface MHC. How come NK cells do not kill RBCs?
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RBCs do not express ligands for NK Activating Receptors
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Transfusion reaction occurs when one individual receives blood that does not match the existing type. It is mediated by antibody recognizing blood antigens on red blood cells. What is the reason T cell response is not elicited?
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ABO antigen is sugar antigen
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