Probiotics Flashcards
what is a probiotic
live microorganisms, when consumes in adequate amounts cause a health benefit on the host
what are the properties required to be classed as a probiotic
- beneficial effect on host
- nonpathogenic and non-toxic
- contain large number of viable cells
- capable of surviving and metabolising in the gut
- remain viable during storage and use
- good sensory properties
- be isolated from same species as host
what are the abilities needed for a probiotic
- beneficial effects
- resistance to bile, hydrochloric acid and pancreatic juice
- GI tract colonisation
- adhere to epithelial cells
- antimicrobial activity
- anticarcinogenic activity
- immune modulation/stimulation
- reduce intestinal permeability
what constantly ‘watches over’ the food and microbial antigen
mucosal immune system
what is the function of the intestinal barrier
tolerance against commensals and immunity against pathogens require intact mechanisms for antigen uptake, recognition, processing and response
what alters the mucosal barrier function
stress
what protects the intestinal cells
intestine have villi and crypts coated with mucus (mucosal layer)
what does the intestine have to protect against pathogens
contain bacteria that prevent bacteria entering
where does selective reabsorption occur in intestine
selective reabsorption into the cell luminal side (contains mucosal layer and bacteria in microflora of them), have a tight junction where molecules can go across selectively to basolateral side
what can break selective reabsorption, what effect does this have
tight junction can be broken by e.g. stress, E.coli
no control of reabsorption causes diarrhoea
what do the paneth cells do
can release antimicrobial molecules into gut lumen
where are the paneth cells
bottom of crypts
where are lymphocytes present
lymphoid follicles
central region of B lymphocytes
lateral region of T lymphocytes
what do M cells do
sample the antigen directly from the lumen and deliver to antigen-presenting cells on basolateral side vis trnscytosis
how is a lymphocyte activated
by a dendritic cell presenting an antigen
where does a activated lymphocyte go
leaves mucosa in lymph
enters bloodstream via thoracic canal/duct
travel to gut
what area do activated lymph colonise
either same mucosa or other mucosal effector sites
what is a peyers patch made of
lymphoid follices
where are peyers patches
in the wall of the small intestine
what is the function of a peyers patch
destroy bacteria - by preventing them to enter the small intestine wall then bloodstream
generate memory lymphocytes for long term immunity
what is MALT
mucosa-associated lymphatic tissue
what covers the peyers patch
special epithelium that contain specialised cells - microfold cells (M cells)
what happens when peyers patch encounter antigen
B-cells and memory cells stimulated
these cells pass to mesenteric lymph nodes - immune response is amplified
what are some mechanisms of probiotic activity
- antimicrobial
- improve environment for beneficial bacteria growth
- make beneficial end product
- reduce harmful end products
- stimulate immune system against pathogens
