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49 Cards in this Set
- Front
- Back
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Why is the GI tract covered by a single layer of epithelium |
To allow efficient nutrient absorption |
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What does the mucosal immune system have to do |
Discriminate between antigens with no pathogenic potential and antigens associated with potentially harmful microbes |
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What is the only disease that doesnt infect mucosal surfaces |
Malaria |
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Name a few diseases that do effect mucosal surfaces |
Diarrhoeal disease Tuberculosis Amoebias Gi worms |
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How much is immune cells in your gut |
70% |
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What is malt |
Mucosal immune system Mucosal associated lymphoid tissue |
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What is the galt snd what is it made up of |
Gastrointestinal associated lymphoid tissue Mesenteric lymph nodes Peyers patches Lamina propria Cryptopatches |
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What are villi covered in |
Epithelial cells |
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What is within the epithelial layer |
Specialised lymphocytes called epithelial lymphocytes- remove dead and damaged cells |
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What does the brush border do |
Increases surface area of epithelial cells |
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What do goblet cells do |
Make mucus- provide a protective gel that contains anti-microbial peptides in it ( the structure and amount of mucus will change when a goblet cell is activated |
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What is the epithelial escalator |
Epithelial cells proliferate doen the crypt of lieberkuhn then they move up to the top ( when it moves up to the top it apoptosis and gets rid of it |
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What happens with the epithelial escalator when you have an infection |
The escalator moves up quicker so the cells cant be there for long and produce more viruses |
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Name mechanical defense in immune response |
Epithelial barrier- held together in tight junctions Peristalsis Diarrhoea |
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Name components of the humoral defense |
Gastric acid Lyzozymes Peroxidase Mucin Anti-microbial peptides Defensins Trefoil proteins |
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What antibodies are present in the gut lumen ‘leaked’ |
Igm ige and igg |
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What is the major antibidy actively secreted in gut lumen and what does it do |
IgA Prevents attachment of bacteria, toxins, viruses, absorption of foreign substances |
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How do bacteria fight IgA |
Produce proteases against the hinge region of IgA eliminating secondary effector function |
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What type of t cells are in the intestine |
Alpha/beta and gamma/delta |
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How much does gamma delta cells take up in man - |
20% |
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Where are alpha beta T cells regulated |
Thymus |
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Where can gamma delta t cells develop extrathymically |
Liver and gut |
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What do gamma delta T cells express |
RAG-1 |
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Gamma delta t cells are homodimeric for what |
CD8 |
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What acts as a component of thr gamma delta CD3 complex |
FcεR1γ chain |
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Are γδ t cells diverse |
No Oligoclonal |
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Why would γδ t celle he important in mucosal defence early in life |
Before αβ T cells and IgA responses are developed |
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In the γδ TCR GENE (VDJ) how slective are the αβ and γδ chains |
γδ chain is much more restrictive |
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what is the main function of γδ Iel ( intraepithelial lymphocytes) |
Surveillance of intestinal epithelial layer against microbial invasion Support of epithelial cell growth and maintenance of epithelial barrier integrity Immunoregulatory |
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For the γδ IEL to stop microbial invasion what does it do |
Cytotoxic activity against microbial pathogens via lysis of epithelial cells Providing b cell help Production of cytokines and chemokine |
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How does γδ IEL support epithelial cell growth and maintenenfe of epithelial barrier integrity |
Production of growth factors Removal of damaged or transformed cells |
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How does γδ IEL work immunoregulatory |
Abrogating/ promoting oral tolerance Production of cytokines Prevent immune responses to the food antigens |
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What is peyers patches |
Organised lymphoid aggregates |
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What are peyers patches made up of |
Specialised follicle associated epithelium ( FAE) Overlying a sub epithelial dome (SED) Overyling multiple B cell follicles that contain germinal centres(GC) Inter follicular regions (IFR) contains T cells, high endothelial venules (HEV) and efferent lymphatics |
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Where does all lymphoid migration occur |
From the-blood across HEV as there are no different lymphatics |
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What happens in the germinal centers |
Where all the b and t cells are talking to each other |
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What are m (microfold cells) |
Primary site of antigen handling in the gut Sepcialised epithelial cells |
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What type of characteristics does m cells have |
Poorly developed brush border No microvilli Thin glycocalyx Absence of hydrolytic enzymes Express MHC class II on basolateral surface Rich in pinocytotic vescles |
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What happens to antigen in the gut |
Lumenal reprocessing Antigen is absorbed but doesn’t evoke a response |
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What is Lumenal preprocessing |
Gastric acid- could denature protein Gastic enzymes Pancreatic proteases |
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How does antigen sampling in the gut happen through dendritic cell route |
Epithelial cells have a tight junction - dendritic cells can modulate the tight junction can poke them through the epithelial cell get the antigen and moves to lymphatic If inflammatory insult will be attracted to that site, this will make epithelial more permeable allow dendritic cell to take them up and present to B and T cell Dendritic cells only do this if they have been told there is a problem through m cells |
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What is epithelial cell route |
Epithelial cell absorbs nutrients across the gut, protein is taken up by epithelial cell then transported in the blood stream To activate the T cell you need MHC and co-stimulatory molecules ( epithelial cells don’t have mhc or co stimulatory molecules |
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What is the M cell route |
Antigen is taken up. m cells express MHC class II and co stimulatiry molecules- if an antigen comes through it can present it |
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What is lymphocyte homing in the intestine |
So cells know where to go when an infection is present |
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How does lymphocyte homing happen |
Has a initial exposure to antigen in the mucosal inductive sites -peyers patches Because it has a signal in it it tells the T cell where to go α4β7(integrins) Mucosal tissue has the corresponding address expressed by the lamina propria (mAdCAM) |
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Name some vascular adhesion molecules |
Madcam-1 Intestinal homing receptor α4β7 |
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What is mADCAM-1 |
Mucosal addressin cell adhesion molecule- selectively expressed on post capillary venules in the lanina propria and gut associated lumphoid tissue such as peryers patches and MLN |
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What does intestinal homing receptor α4β7 do |
Heterodimeruc integrin adhesion receptor fanily expressed in high levels on intestinal memory and effector cells, hinds to MadCAM-1 |
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Why do we need to know of the mechanisms of mucosal immunity? |
Mist pathogens enter via mucosal route Understand the mechanisms so you can devise strategies against inflammatory bowel disease |
