Mucosal Immunity Basic Science Flashcards
What are the physiological functions of mucosal tissues?
- gas exchange
- food absorption
- sensory activities
- reproduction
What is the junction between mucosal cells called?
Tight Junction
List the mucosal tissues of the GI system?
- oral cavity
- oesophagus
- stomach
- intestine
What are the 3 distinctive anatomical features of the GUT mucosal immune system?
- intimate relationship between mucosal epithelia and lymphoid tissue
- organised lymphoid structures unique to mucosal sites
- specialised antigen uptake mechanissm
What are 2 distinctive effector mechanisms of Gut mucosal immune system?
- activated/memory T cell predominate
- “natural” effector/regulatory T cells
What are 2 distinctive features of the immunoregulatory environment of the gut mucosal immune system?
- active down regulation of immune response
- inhibitory macrophages and tolerising dendritic cells
What are Peyer’s patches?
“essentially the lymph nodes of intestine”
-covered by epithelial layer containing specialised cells called M cells (in dome) which have characteristic membrane ruffles (M=Microvilli)
What immune cells are inside Peyer’s Patches?
T cells (with germinal centre) and dendritic cells
What do M cells do?
M cells endocytose and phagocytose antigens. antigen is transported across the M cells in vesicles and released and then bound to dendritic cells
How do dendritic cells sometimes capture antigen from lumen of gut?
By extending processes across epithelial layer
What are the 2 distinct layers of the mucosal immune system and what immune cells do they contain?
- lamina propria: CD4 T cells, dendritic cells, macrophages, mast cells, plasma cells
- epithelial layer: CD8 T cell, dendritic cell
What immunoglobulins does the gut produce and approx. how much of each?
- IgA 80%
- IgM 15%
- IgG 5%
What immunoglobulins does the body produce and how much of each?
- IgG 80%
- IgM 15%
- IgA 5%
How does IgA get to lumen?
IgA bound to receptor (poly-Ig receptor) which are endocytosed by cell and transcytosed across cell and released with secretory component attached
What is the function of the secretory component bound to released IgA?
To protect the secretory component from proteolytic enzymes in lumen
What are the specialised T cells of the gut and where do they lie?
either in the epithelium or in between epithelial cells
What 3 substances inhibit dendritic cell maturation in the presence of commensal bacteria?
PGE2, TSLP, TGF-beta
What are the mucosal tissues of the respiratory system?
- trachea
- lungs
What parts of the eye are mucosal tissue?
- conjunctiva
- lachrymal gland
What gland in the face is mucosal tissue?
salivary gland
What parts of the uro-genital system are mucosal tissue?
- kidneys
- uterus
- bladder
- vagina
How do T cells enter the Peyer’s Patches and what homing receptors are involved?
They enter from blood vessels directed by CCR7 and L-selectin
What causes a T cell to become activated?
When they encounter antigen they become activated by dendritic cells
Where do activated T cells go from Peyer’s patch?
They drain via the mesenteric lymph nodes to the thoracic duct and return to the gut via the bloodstream
What activated T cells home to the lamina propria and epithelium of the small intestine?
Activated T cells expressing alpha4:beta7 integrin and CCR9
What do gut-homing effector T cells bind onto epithelium when in blood vessel and what do the gut eptihelial cells express for these T cells?
- MAdCAM-1
- express cytokines
