Immunological functions of the alimentary tract

Question 1

What does the innate immune system do?

Answer 1

→Prevents infection and avoids disease
→Non-specific
→No memory
→It prevents disease

Question 2

What is the innate immune system mediated by?

Answer 2

→Mediated by : macrophages, epithelial barriers and secretions

Question 3

What does the adaptive immune system do?

Answer 3

→Responds to infection and prevents disease
→Highly specific response to targeted microbe
→Memory

Question 4

What is the adaptive immune system mediated by?

Answer 4

→Mediated by : lymphocytes and antibodies

Responds to infection

Question 5

What is involved in the systemic immune system?

Answer 5

→Bone marrow
→spleen
→thymus
→ lymph system
→ blood circulation

Question 6

What is involved in the mucosal immune system?

Answer 6

→ Mucous membranes 
→  Eyes
→ nose
→  mouth
→ lungs
→ gut
→ genitourinary tract

Question 7

What does the gut do to prevent colonization?

Answer 7

→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.

Question 8

What are the mucosal surfaces?

Answer 8

→oral
→ nasal 
→lacrimal surfaces
→gastrointestinal tract
→ bronchial tract
→genitourinary tract 
→ mammary glands

Question 9

What do innate mechanisms of protection do?

Answer 9

→Mucin
→ peristalsis
→ antimicrobial peptides 
→ proteins
 e.g lysozyme, lactoferrin and phagocytes

Question 10

What does the adaptive immune system include?

Answer 10

→Mucosal/secretory immune system

Question 11

What must the adaptive immune system do?

Answer 11

→Must discriminate between harmful pathogens and harmless antigens - food and commensal bacteria

Question 12

What does the immunological mucosal barrier produce?

Answer 12

→secretory IgA/IgM/IgG

Question 13

?What is the tooth-gum junction like and why?

Answer 13

→The junction where the tooth comes through the gum is leaky.
→The blood vessels are under high pressure and are pushing serum out.

Question 14

What are the lymphoid tissues in the gut ?

Answer 14

→Intraepithelial lymphocytes
→Lymphocytes and macrophages are scattered in the lamina propria
→Peyer’s patches

Question 15

What is the gut lined with and why?

Answer 15

→The gut is lined by columnar epithelial cells which are ciliated to move the mucus and the bacteria along.

Question 16

What is under the epithelial cells?

Answer 16

→sub mucosal layers

Question 17

What is underneath the mucosal layers?

Answer 17

→Underneath this are the blood vessels and lymph nodes.

Question 18

What are the routes of entry of a pathogen into the blood?

Answer 18

→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

Question 19

What is a Peyer’s patch ?

Answer 19

→The lump will have a collection of WBCs underneath it

→It is the lymph node of the mucosal immune system

Question 20

What does a Peyer’s patch do?

Answer 20

→The peyer’s patches constantly sample what is in the gut

→It is looking for anything that should not be there

Question 21

What has to occur to generate an immune response?

Answer 21

→In order to generate an immune response, the immunogen has to be taken up by a peyer’s patch otherwise you get nothing

Question 22

What is the arrangement of lymphocytes inside the M cell?

Answer 22

→ the lymphocytes push up inside the M cells

Question 23

Why is the lymphocyte arranged inside the M cell?

Answer 23

→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.

Question 24

What do the M cells target?

Answer 24

→Particles and macromolecules

→Viruses

→Parasites

→Bacteria

Question 25

What happens once the pathogen has entered a Peyer’s patch?

Answer 25

→ 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

Question 26

What happens after the WBC matures in the lymph node?

Answer 26

→ goes back to the gut to provide antibodies

→ also goes everywhere in the mucosal immune system

Question 27

What are mucosal antibodies and where are they found?

Answer 27

→Predominantly Secretory IgA

→Found in all secretions and breast milk

Question 28

What provides passive immune protection in newborns?

Answer 28

→mucosal antibodies

Question 29

What is the mechanism of action of IgG?

Answer 29

→Binding to key functional sites on microbes and toxins
→Agglutination
→Induce Flammarion
→Recruit immune cells

Question 30

What is the mechanism of action of SIgA?

Answer 30

→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

Question 31

Why is IgG undesirable in inflammatory diseases?

Answer 31

→ It produces more inflammation

Question 32

Why is mucosal immunity not given as a vaccine?

Answer 32

→ Good response but doesn’t last as long

Question 33

How are GM potatoes with vaccines made?

Answer 33

→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

Question 34

Why are mucosal antigens not given orally?

Answer 34

→If an antigen is first encountered through the mucosal immune system, the systemic immune system may become unresponsive (tolerised) to that antigen.

Question 35

What can orally delivered antigens do?

Answer 35

→suppress systemic immunity