Immunity of the Alimentary Tract Flashcards
How is the mucosal immune system different from systemic immunity?
Systemic immunity: Bone marrow, spleen, thymus lymph system, blood circulation
Mucosal immunity: protects the mucosal surfaces of your body
Mucous membranes – eyes, nose, mouth, lungs, gut, genitourinary tract.
Describe the mucosal immune system
All sites are normally colonised by microbes
Main route of entry for infectious microorganisms
Large surface area specialised for absorption.
Gut ~ 200m2 Skin ~2m2
What are the innate vs adaptive mechanisms of the body in the mucosal immune system?
Innate protection:
Mucin in saliva makes it harder for a pathogen to enter the body, peristalsis of swallowed mucus gives extra protection.
Antimicrobial peptides and proteins e.g. lysozyme, lactoferrin; phagocytes in mucosal membranes
Adaptive mechanisms are also present: mucosal/secretory immune system secretes IgA,M,G
What are peyers patches?
The villi is briefly interrupted= peyers patch
The Peyers patch is covered by specialised epithelim and M cells
The distance between M cells and the gut fluid is v small which enables the M cell to easily sample the fluid of the gut
Peyers patches mediate immunity and help antibody activation. The site of stimulation is usually at specialised sites in GALT BALT and NALT peyers patches. Immune cells then migrate to the lympatic drainage
What are the main m cell targets for uptake?
Particles and macromolecules: eg cholera toxin, latex particles ferritin.
Viruses: eg poliovirus, HIV
Parasites: eg Cryptosporidium
Bacteria: eg Cholera, salmonella, E. coli
What is the journey of immune cells in the common mucosal immune system?
Basically the B cell will always target the glands of the mucosal system
What are the main antibodies in the mucosal system?
Predominantly Secretory IgA
Found in all secretions and breast milk
Provide passive immune protection in new-born infants
IgA antibodies dimerise with a joining chain. An overcoat wraps around the antibody and prevents it from being degraded
What is the mechanism of action of SIgA?
SIgA is expressed at all mucosal sites
Binds to key functional sites on microbes and toxins
Much better Agglutination
What are some examples of oral immunisation?
Attenuated virus (eg polio)
Attenuated recombinant bacterial mutants (eg Salmonella typhi)
Mucosal adjuvants (eg cholera toxin)
Liposomes, microspheres,
Capsules
Transgenic edible plants- eg Grow plants which express hepatitis vaccine and harvest edible tissue.
What is the disadvantages of mucosal/oral immunisation?
Hay a lack of a secondary response in mucosal immunisation
Also, If an antigen is first encountered thru the mucosal system, the systemic immune system may become unresponsive (tolerised) to that antigen.
What is the concept of oral tolerance?
Orally delivered antigens can suppress systemic immunity
This is a natural, necessary mechanism to prevent immune reactions to food and useful commensals.
What is the difference between oral tolerance and conventional immunisation
Tolerance is soluble antigens, with repeated sustained, and high does
On the other hand, conventional vaccination is with an antigen/adjuvant or other formulations. It is a limited number of low dose immunisations
