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 is involved in the systemic immune system?
→Bone marrow →spleen →thymus → lymph system → blood circulation
What is 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 Flammarion
→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
