Immunological Functions of the Alimentary Tract Flashcards
What does the innate immune system do?
→Prevents infection and avoids disease
→Non-specific
→No memory
→It prevents disease
What is the innate immune system mediated by?
→Mediated by : macrophages, epithelial barriers and secretions
What does the adaptive immune system do?
→Responds to infection and prevents disease
→Highly specific response to targeted microbe
→Memory
What is the adaptive immune system mediated by?
→Mediated by : lymphocytes and antibodies
Responds to infection
What structures are involved in the systemic immune system?
→Bone marrow →spleen →thymus → lymph system → blood circulation
What structures are involved in the mucosal immune system?
→ Mucous membranes → Eyes → nose → mouth → lungs → gut → genitourinary tract
What does the gut do to prevent colonization?
→In the gut the peristaltic waves are always moving material through the gut so the bacteria do not have a chance to colonize the bacteria.
What are the mucosal surfaces?
→oral → nasal →lacrimal surfaces →gastrointestinal tract → bronchial tract →genitourinary tract → mammary glands
What do innate mechanisms of protection do?
→Mucin → peristalsis → antimicrobial peptides → proteins e.g lysozyme, lactoferrin and phagocytes
What does the adaptive immune system include?
→Mucosal/secretory immune system
What must the adaptive immune system do?
→Must discriminate between harmful pathogens and harmless antigens - food and commensal bacteria
What does the immunological mucosal barrier produce?
→secretory IgA/IgM/IgG
What is the tooth-gum junction like and why?
→The junction where the tooth comes through the gum is leaky.
→The blood vessels are under high pressure and are pushing serum out.
What are the lymphoid tissues in the gut ?
→Intraepithelial lymphocytes
→Lymphocytes and macrophages are scattered in the lamina propria
→Peyer’s patches
What is the gut lined with and why?
→The gut is lined by columnar epithelial cells which are ciliated to move the mucus and the bacteria along.
What is under the epithelial cells?
→sub mucosal layers
What is underneath the mucosal layers?
→Underneath this are the blood vessels and lymph nodes.
What are the routes of entry of a pathogen into the blood?
→Any sort of breach of the epithelium
E.g. a stomach ulcer
→Some can squeeze across the epithelial junctions
Or they can join to our own cells (langerhan cell) which will carry the pathogen across
What is a Peyer’s patch ?
→The lump will have a collection of WBCs underneath it
→It is the lymph node of the mucosal immune system
What does a Peyer’s patch do?
→The peyer’s patches constantly sample what is in the gut
→It is looking for anything that should not be there
What has to occur to generate an immune response?
In order to generate an immune response, the immunogen has to be taken up by a peyer’s patch otherwise you get nothing
What is the arrangement of lymphocytes inside the M cell?
→ the lymphocytes push up inside the M cells
Why is the lymphocyte arranged inside the M cell?
→The gap between the external surface of the gut and the first lymphocyte that it encounters is very very small
→So a pathogen just has to cross the first barrier and then it will come into contact with the immune system.
What do the M cells target?
→Particles and macromolecules
→Viruses
→Parasites
→Bacteria
What happens once the pathogen has entered a Peyer’s patch?
→ passed through to the first white blood cell
→Once the WBC encounters the pathogen, it migrates through the tissue and into the lymph drainage
→ Starts to develop in the first lymph node (mesenteric)
→They mature in the lymph node and move back into the blood
What happens after the WBC matures in the lymph node?
→ goes back to the gut to provide antibodies
→ also goes everywhere in the mucosal immune system
What are mucosal antibodies and where are they found?
→Predominantly Secretory IgA
→Found in all secretions and breast milk
What provides passive immune protection in newborns?
→mucosal antibodies
What is the mechanism of action of IgG?
→Binding to key functional sites on microbes and toxins
→Agglutination
→Induce inflammation
→Recruit immune cells
What is the mechanism of action of SIgA?
→Binding to key functional sites on microbes and toxins →Agglutination (much better) →Immune exclusion →Intra-cellular neutralisation →Virus excretion →Interactions with non-specific factors →lysozyme, lactoferrin, peroxidases
Why is IgG undesirable in inflammatory diseases?
→ It produces more inflammation
Why is mucosal immunity not given as a vaccine?
→ Good response but doesn’t last as long
How are GM potatoes with vaccines made?
→The Hep B surface antigen gene is transferred from yeast into a plant cell
→Potato is used as a prototype
→Potato plants are regenerate from transformed cells
→Hepatitis vaccine is correctly expressed by potato plans
→GM potatoes are harvested that contain the hepatitis vaccine
Why are mucosal antigens not given orally?
→If an antigen is first encountered through the mucosal immune system, the systemic immune system may become unresponsive (tolerised) to that antigen.
What can orally delivered antigens do?
→suppress systemic immunity
What are the practical considerations of oral tolerance?
→Tolerance to dietary foods, breakdown to food allergy.
→Oral vaccination and safety
→Treatment and prevention of autoimmune diseases-
How do sIgA dimerised?
→by joining component so that it recognises 4 antigens
Give examples of pathogens taken up by m-cells
cholera toxin, latex particles, horseradish peroxidase, ferritin.
→poliovirus, HIV
→Cryptosporidium
→Cholera, salmonella, Campylobacter Yersinia, Shigella, E. coli
Describe the sources of serum, saliva, and local antibodies in the oral cavity
→lymphoid tissue →peripheral blood →gingival focus of leucocytes →salivary gland →crevicular fluid
