Immunological features of the alimentary tract Flashcards
the mouth is what?
a major portal for infection
what are located at the top of the throat?
Tonsils and adenoids
how can we split the immune system up?
innate vs adaptive
mucosal vs systemic
innate immune system
prevents you getting ill in the first place
prevents infection and avoids disease
non-specific
no memory
mediated by: macrophages, epithelial barriers, secretions…
adaptive immune system
responds to infection and prevents disease
highly specific response to targeted microbe
memory - allow quicker and more powerful response
mediated by:
Lymphocytes, antibodies
how might the bacteria end up in the faeces?
peristaltic waves push the bacteria
systemic immunity
bone marrow, spleen, thymus lymph system, blood circulation
part that actually responds to an injected vaccine, or a pathogen that has already breached the first epithelial barrier
mucosal immunity
protects all the wet parts of the body, external parts of the body covered in mucus membranes - oral, nasal, bronchial tract, lacrimal surfaces, eyes, gut, GI tract, genitourinary tract.
all the mucosal membranes are colonized by bacteria, most of them by good bacteria
the mucosal surfaces are what?
main route of entry for infectious microorganisms
although the gut has a large SA for absorption, why might this be a problem?
increases the surface area a microbe infecting it
so, it’s important we have a mucosal immune system specifically for protecting those mucosal surfaces
innate and adaptive mechanisms of the mucosal immune system
Innate mechanisms of protection include:
mucin, peristalsis, antimicrobial peptides and proteins e.g. lysozyme, lactoferrin; phagocytes
Adaptive mechanisms:
mucosal/secretory immune system
what is saliva made up of?
80% water
19% mucus - mucus is what makes it slippery
1% enzymes
also antibodies
lysozyme
breaks down bacteria phagocytes
lactoferrin
hoards iron to stop bacterial growth
phagocytes
engulf microbes
the mucosal immune system must do what?
discriminate between harmful pathogens and harmless antigens – foods and commensal bacteria
what happens when the process of distinguishing between good and bad bacteria breaks down?
develop food allergies
name some mucosal barriers
innate (natural barriers, eg. stomach)
- Mucin
- Peristalsis
- Proteolysis
- Microvillus membrane
immunological
- Secretory IgA/IgM
- IgG
gingival tissues
have an exudate going on the surface of the gums – serum exudate from the blood system
gingival fluid contains all the blood components except for RBCs (so antibodies, WBCs and phagocytes)
explain the contribution of the systemic immunity from the blood circulation into the mouth
all the solution in the mouth is predominantly from saliva
but, in the mouth you have a hard tissue that has its origins in the systemic system, and it breaks the epithelial layer to come into the mucosal layer
the junction where the tooth comes through the gum is a site of leakiness
all the blood vessels in this area are high pressure, exudate comes out - in this exudate you can find antibodies and white blood cells that have originated from blood
IGA deficiency
the mucosal immune system doesn’t work properly, and the exudate they get through the epithelial layer from the blood seems to increase
this is because the body recognises they don’t have mucosal immunity and compensates by increasing systemic immunity- so, they don’t get so many infections.
cel layers of the gut
the gut is lined by a single layer of columnar epithelial cells (important because you don’t want to food to have to get through multiple thick layers- adaptation)
the cells are ciliated which moves along the mucus and bacteria
underneath the epithelial layer is submucosa, and once you past this layer you can access the lymph nodes and blood vessels.
how can a bug in the lumen of the gut past these barriers and cause infection (i.e. into the bloodstream)?
- Breach of the epithelial layer (gastric/duodenal ulcer/inflammatory disease like Chrone’s)
- Attaching to dendritic cells (professional APC’s) but not getting engulfed, and then when the dendritic cell decides to come back in the virus is bought through the epithelial barrier in tact
- Some pathogens squeeze across between the epithelial junctions