mucosal immunity Flashcards
physiological function of mucosal tissue
gas exchange food absorbtion sensory activity reproduction all functions critical to life
mucosal tissue
highly vulnerable due to fragility and permeability
require effective defence mechanisms
portals of entry for non-pathogenic antigens
mesentry lymph nodes
lymph nodes where all primary immune response occurs
found in the gut
afferent lymphatic vessel
bring antigen into lymph node
via dendrite cells
efferent lymphatic vessel
where activated cells leave and entr blood supply
anatomy of gut mucosal immune system
intimate relationship between mucosal epithelia and lymphoid tissue
organised lymphoid structures unique to mucosal sites]
specialised antigen uptake mechanisms
effector mechanisms of gut mucosal immune system
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immunoregulatory environment of gut mucosal system
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lamina propria
contains every cell you can imagine
where effector function happens
peyers pathc
acessential to how immune response of the gut works
covered by an epithelial layer specialised cells called M cells which have characteristic membrane ruffles
peyers patch anatomy function
huge absorptive cap
membrane ruffles- increase SA of the cell
goblet cells
create mucous
where M cells loacted
the dome
how do M cells work
M cells take up antigen by endocytosis and phagoscytosis
antigen is transported across the M cells in vesicles and released at the basal surface
antigen is bound by dendritic cells which active T cells
another role of dendritic cell in gut
can extend processes across the epithelial layer to capture antigen from the lumen of the gut
also occur in the lung
intra epithelial cells
sit in epithelial mucosa
acting as monitors monitering infection and death of epithelial cells
what in the mucosal immune system
consists of two distinct compartments
epithelium and lamina propria
adaptive response in mucsal layer
T cells enter payers patches from blood vessels directed by the homing receptors CCR7 and L-selectin
T cells in the peyers patch encounter antigen transported across M cells and become activated by dendritic cells
activated T cells drain via mesenteric lymph nodes to the thoracic duct and return to the gut via the blood stream
activated T cells expressing a4B7 integrin and CCR9 home to the lamina propria and intestinal epithelium if the small intestine
overall mucous immunity
medcam is found in the vascalature of other mucosal sites
lymphocytes primed in the gut can migrate to other mucosal sites
passive immunity transfer in breast milk
what antibodies found in mucosal intestine
IgA
IgM
IgG
how IgA works
binding of IgA to receptors on basolateral face of epithelial cell
endocytosis
transcytosis of apical face of epithelial cell
release of IgA dimer at the apical face of epithelial cell
overall function of IgA
secreted Iga ON THE GUT SURFACE can binds and neutralise pathogens and toxins
IgA is able to bind and neutralise antigens internalised in endosomes
IgA can export toxins and pathogens from the lamina propria while being secreted
intraepithelial lymphocytes
fully activate containing full killing machinery don’t need activation
restricted antigen receptor repertoire- don’t express normal TCR
expression of aE;B7 integrin anchors them in the epithelium
2 types with different recognition mechansisms
where intraepithelial lymphocytes are found
lie withint he epithelial ,lining of the gut
they are CD8 positive T cells
purpose of intraepithelial lymphoctes
virus infects mucosal epithelium cells infected cell displays peptide to CD8 IEL via MHC class 1
activated IEL lkills infected epithelial cell by perforin/granzyme and Fas-dependant pathways
stress in epithelium
occurs are a result of infection, damage, or toxic peptides and express MIC-A and MIC-B
NKG2D on IELs bind to MIC-A,B and activate the IEL
CD8 himodimers also bind to TL
activated IEL kills the stressed cell via perforin/granzyme pathway
how is the balance between protective immunity and homeostasis maintained
there is a sophisticated means of discriminating between pathogen and innocuous antigens
default response to oal administration of protein state of specific peripheral unresponseiveness- oral tolerance
T cell and IgE mediated responses are inhibited more than serum IgG reponses both locally and systemically
proposed mechanism of mucosal hyperresponsiveness
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what happens when muscoal immunity becomes disregulated
nuon
what happens to infected dedritic cells
they shuttle visures from the site of exposure to the regional lymph nodes where they concentrate virus partcicles and infect CD4+Tcells
wgat di you give someone with crohns disease
immunosuppresatns
food allergy
yype 1 hypersensitivity reaction initiated by crosslink of allergen specific IgE on the surface of the mast cells with the specific allergen
memory response- immune system must be primed
