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40 Cards in this Set
- Front
- Back
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What is Ag Capture and Presentation?
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The events that APCs ingest encountered foreign matters and bring to lymphocytes
It particularly applies in activating T cells |
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Why is it important to know about Ag capture and Presentation?
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Cell mediated immunity is critical in dealing with adverse episodes such as viral infection
Major player in CMI T cells only recognize antigen in the format of peptide epitope presented by MHC on APCs |
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What are the sites of antigen capture?
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1. Skin-langerhans
2. Oral-Respiratory Alveolar Macrophages or GI where M cells present antigen to lymphocytes 3. Urinary tract & reproductive organs- Dendritic cells 4. Injection a. Spleen-captures microbes in blood b. Tissue-specific Macrophages-captures microbes in tissues |
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Blood borne antigens are captured and presented in?
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Spleen
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Antigens entering from other routes are captures by what?
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Tissue-specific Macrophage and DC and brought to present in lymph node via lymphatic vessels
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What are the 2 sites in the spleen?
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1. T cell zone-PALS
2. B cell zone-Marginal zone & germinal center |
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B cell zone has two parts?
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1. Follicle (naive)
2. Germinal Center (activated) |
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T cell zone is also called the?
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Paracortex
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Where do the naive lymphocytes enter the lymph node?
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Artery
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Where do the T cells enter the lymph node?
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HEV
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The antigen enters from?
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The afferent lymphatic vessel
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The activated lymphocyte exits via?
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efferent lymhpatic vessel
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B cells recognize antigens using what type of receptors?
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B Cell Receptor (BCR), i.e. immunoglobulin (Ig) molecules on their surface (mIg)
-remember if see “m” in front of Ig it refers to B cells |
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B cells recognize what types of antigens?
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Carbs
Lipids ss or ds DNA or RNA Protein |
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Can B cells recognize antigens without APC?
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Yes except:
Follicular Dendritic Cell (FDC) functions as APC for B cell in Affinity Maturation in the germinal center |
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Can T cells recognize antigens without APC?
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No, need APCs
But need help from MHC, generated by APC, which holds the peptides so T cells can recognize them. |
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What type of MHC is expressed on all nucleated cells?
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MHC I
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What expresses both MHC I and MHC II?
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APCs
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MHC I stimulates what type of T cells?
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CD8+
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MHC II stimulates what type of T cells?
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CD4+
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What are the APC cells?
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Dendritic cell
Macrophages B cells |
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What APC mediates between innate and adaptive?
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Macrophage
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What happens once an APC takes up an antigen?
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1. Activated, immature DC migrate to lymph node via lymphatic vessel by downgrading chemokine receptors. (chemokine holds DC in place)
2. DC starts to mature during migration, start to digest microbe 3. Mature DC presents antigen to naive T cell in paracortex of lymph node. |
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Anchor residue of MHC
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Amino acid that fits in the MHC pockets and confers stable binding
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BCR
TCR |
B cell receptor
T cell receptor on B/T cell where MHC interacts with. |
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Peptide epitope cannot expresse themselves without MHC. Then can T cells be activated.
APC & T cells must have the same MHC molecules for T cell activation |
MHC Restriction
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The MHC that is expressed only on APCs?
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MHC II
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Where is the cleft on MHC I?
What part on MHC I binds CD8 on T cells? What is the peptide length? |
alpha 1 - alpha 2
Where peptide interacts with MHC. alpha 3 8-10aa |
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In what MHC are the alpha and beta chains not connected?
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MHC II
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Where is the cleft on MHC II?
What part on MHC II binds CD4 on T cells? What is the peptide length? |
alpha 1 - beta 1
Where peptide interacts with MHC. Beta 2 10-30 aa |
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What are the characteristics of the peptide antigen on MHC?
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1. Only linear & processed peptides bind to MHC.
2. Binding of peptide stablilizes expression of MHC on surface 3. One peptide/MHC per time 4. Different peptides can bind to one MHC. 5. MHC binds to self and non self |
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HLA
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HLA: Human Leukocyte Antigen
Gene loci is on Chromosome 6 |
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MHC I has what type of HLA?
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MHC I: HLA-A, -B, -C
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MHC II has what type of HLA?
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MHC II: HLA-DP, -DQ, -DR
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Nonpolymorphic MHC genes?
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DM: MHC II assembly
Proteasome and TAP: MHC I assembly Complement: C2, C4, Factor B Cytokine: TNF, LT, LTb |
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Does every nucleated cell in one individual expresses the same MHC molecules
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Yes
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How is MHC inherited?
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Inherited on two haplotypes, one from each parent.
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The unit which MHC is transmitted genetically
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Haplotype
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How are paternal and maternal haplotype expressed?
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Codominance
both alleles expressed |
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Why is polymorphism important for MHC?
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Polymorphism provides a mechanism to promote population survival by maximizing exposure of danger to defense system
MHC is the most polymorphic gene in human |
