Mucosal Immunology Flashcards
What are the layers of the mucosa (3)
- one or more layers of epithelium
- Basement membrane
- Lamina propria (loose connective tissue rich in cells including fibroblasts, lymphocytes, plasma cells, macrophages and mast cells)
What is the function of mucous membranes (2)
- stop pathogen and foreign material entry (1st layer of protection)
- Help keep body hydrated
What cells secrete mucus and where are they found (3)
Goblet cells secrete mucins
type of modified columnar epithelial cells found in different parts of the respiratory, reproduction and gastro tracts
Where are immune cells found in mucus membranes (2)
embeded in epithelium +/or loosly in the lamina proproa
What are MALTs
sites where adaptove immune responses are generated in mucosal tissues
what are the 4 types of MALT
GALT (peyes patches, isolated lympoid follicles, vermiform apendix, tonsils, mesenteric lymph nodes)
NALT
BALT
VALT
Movemebt of t + b cells thru peyers patches/isolated lympoif follicles
activate t + b cells
-once activated they can move to epithelium etc
Where are peyers patches found
Aggregated lymphoid nodules found in the small intestine (mainly in the distal jejunum and ileum)
What MALT is waldeyers tonsillar ring part of and 4 types
Considered part of NALT (generate responses to antigens in nasopharynx)
-Pharyngeal tonsil, tubal tonsil, palantine tonsil, lingual tonsil
What are the mucus membrane instrinsic barriers (6)
- Mucus
- Junctional proteins (tight packed)
- IL-22 ( keeps junctional pros working)
- Mucosal antibodies (iGa)
- Antimicrobial peptides
- microorgansims
How do antigens get thru mucosal tissue
Can either diffuse of be transfered via specialized epithelial cells (m cells)
What happens to antigens once they move across the mucosal tissue
Local APCs sample mucosal antigens and activate t cells in nearby MALTS (payers patches etc) ( can also be activated by mucosal b cells)
What is the inductive vs effector site when generating a immune response
Inductive sites- MALTS (where mucosal adaptove immune responses are activated)
Effector sites- where the activated mucosal t cells and b cells exert their function (could be close or far away but usually mucosal t cells are primed to move back to mucosal sites after activation)
When t cells are activated in presense of RA(retinoic acid) (found in gut) what is expressed
integrin a4B7 and chemokine receptor ccr9
What is the function of integrin A4B7 and chemokine receptor ccr9 on MALT activated t cells
- CCR9 is specific to CCL25 which is abundant in the gut (chemotaxis)
- A4B7 binds to madcam-1 which is on vascular endothelial cells (allows t cells entry back to mucosal sites)
What cells convert Vit A to retinoic acid
in specialized cells that express CD103
what are 3 ways activated mucosal t cells can be found
- Intraepitheleal lymphocytes
- Isolated lymphocytes in lamina propria
- effector cells in organized MALTS
Ratio of CD4 to CD8 t cells in lamina propria
CD4:CD8 is 2:1
similar to non mucosal peripheral lympoid t cells
Ratio of CD4 to CD8 t cells when embeded in mucus membrane (intraepitheleal lymphocytes)
CD4:CD8 = 1:8
How do intraepithel lymphocytes embed into the epithelium
Express aE:b7(cd103) whihc binds to e cadherin on epithelial cells allowing them to embed
Function of intraepitheleal lymphocytes
dont need priming by APCs
-upon encountering antigens they immediately release cytokines and cause killing of infected/stressed cells
Where are naive mucosal b cells found and what activates them
reside in MALTS and await activation by actiated t cels
what is the dominant class of antibody produced at mucosal surfaces and what is the primary function
- IgA produced by plasma cells
- primarily function in neutralization
what is the structure of secretory IgA in mucosa
Dimeric (two identigal igAs linked by J chain
What is the movement of Secretory IgA (+ what is the receptor name)
Moves from basolateral side of epithelium to lumen by polymeric immunoglobulin receptor expressed on basolateral side
What are the components of secratory Iga
Dimetrc IgA with part of the polymeric immunoglobulin receptor still attached
What is the mc primary immunodeficiency disease and what are they more susceptible to
Selective IgA deficiency
-increased incidence of upper and lower respiratory gastro infections
DCs in the gut that express cd103 (aeb7) also act as what
can induce iTREG formation against non self antigens that enter the gut
(oral tolerance against food antigens/gut bac)
