3.2 Mucosal immunity

Question 1

___ and ____ are susceptible to infection

Answer 1

External surfaces
Skin ( stratified squamous, thick layers, good for defense)

Mucous membranes: are particularly more due susceptible (easily infected) since they are thin Walled to allow physiological function
-respiratory tract: gaseous exchange
- GIT: absorption of nutrients

Question 2

Innate immunity at mucosal sites:

Answer 2

Question 3

Protect the respiratory epithelium:

Answer 3

Mucociliary escalator and alveolar macrophages

Question 4

Alveolar =

Answer 4

Gaseous exchange

Question 5

In milk-fed animals
e.g. calves, the GIT is colonised by

Answer 5

lactobacilli that produce lactic and butyric acid which have antimicrobial properties

Question 6

Treatment of rabbits with penicillin can lead to?

Answer 6

fatal enterotoxaemia - can wipe out microbiome allowing gut to repopulate with bad species like clostridium

Question 7

Gamma:delta T cells are found where?

Answer 7

Found beneath enteric mucosal epithelium

Question 8

Gamma: delta T cells

Answer 8

Invariant receptors
– unlike conventional αβ T cells

Do not require MHC
– recognise stress proteins / symptoms

Question 9

Gamma delta (gd) T cells are important for innate protection of mucosa in

Answer 9

in farm animals (90% of T cells in pigs are gd)

Question 10

Mucosal-associated lymphoid tissues (MALT): ( common mucosal system)

Answer 10

– Tonsils
– Peyers patches
– Mesenteric lymph nodes
– Bronchial-associated lymphoid tissue
– Mammary gland lymphoid tissue

Question 11

Antigen stimulation at one site leads to

Answer 11

recruitment and response in ALL mucosal lymphoid tissue.

Question 12

Adaptive immunity: Antigen delivered via non-mucosal route

Answer 12

Ex: vaccine given SQ or IM
– IgM and IgG antibodies predominate
– Systemic protection from infection

Question 13

Antigen delivered via mucosal route

Answer 13

– IgA and IgE antibodies predominate
– Mucosal protection from infection

Question 14

Antigen exposure in the gut is usually recognised by

Answer 14

cells in Peyer’s patches in the ileum

Question 15

Antigen exposure in the gut is usually recognised by

Answer 15

by cells in Peyer’s patches in the ileum

Question 16

microfold (M) cells:

Answer 16

Specialised epithelial cells that sample luminal contents and transport antigen to underlying lymphoid tissue

Question 17

M cell process:

Answer 17

Question 18

Adaptive immunity in MALT: B cell response

Answer 18

– Mainly IgA production
– IgE production important against parasites
– Some IgG in case of systemic spread of infection

Question 19

Adaptive immunity in MALT: T cell response

Answer 19

Mainly T helper type 2 (TH2) and TH3 cells
- TH2 > IL-4: stimulates B cell class-switching to IgE
- TH3 > TGF-beta: stimulates B cell class switching to IgA

Question 20

IgA is produced by

Answer 20

plasma cells in submucosa and is transported by epithelial cells into lumen

Question 21

IgA functions:

Answer 21

NEUTRALISING antibody on the mucosal surface
- Viruses
- Bacterial adhesins
- Microbial toxins

Question 22

IgA protects against

Answer 22

infection (neutralisation)

Question 23

___ and ___ are effective if epithelial barrier is breached

Answer 23

IgE and IgG

Question 24

IgE allows

Answer 24

submucosal mast cells and eosinophils to detect and expel helmith parasites

Question 25

Problem with IgE

Answer 25

can lead to dietary hypersensitivity

Question 26

The main function of the GIT is?

Answer 26

Absorption of nutrients

Question 27

The MALT must be able to

Answer 27

distinguish food antigens from pathogen antigens

Question 28

Dietary proteins do not express

Answer 28

PAMPs: – Initial activation which is inhibited following generation of regulatory T cells producing immunosuppressive cytokines - mucosal tolerance Exposure to pathogens leads to innate respond and inflammation in the GIT – PRR detection of PAMPs by cells of innate immunity – Pro-inflammatory cytokines amplify adaptive response

Question 29

“sample” the liminal contents for mucosal tolerance

Answer 29

Dendritic cells

Question 30

Mucosal tolerance: Harmless antigens

Answer 30

Produces immunosuppressive cytokines to switch off the immune response

Question 31

Gluten-sensitive enteropathy (Coeliac disease)

Answer 31

• Dietary allergy to gluten • Irish setter dogs • Feed a gluten-free diet

Question 32

Migration of B cells from the MALT to the mammary gland and secretion of antibodies is important for neonatal immunity:

Answer 32

- Neonatal immune system is poorly developed - Mucosal surfaces of newborn animals are particularly vulnerable to infection - Passive transfer of maternal antibody in colostrum & milk protects neonates from pathogens

Question 33

Farm animal species rely on transfer of antibodies in

Answer 33

Colostrum and milk

Question 34

Colostrum is rich in

Answer 34

IgG

Question 35

Milk contains predominantly

Answer 35

IgA (mucosal protection)

Question 36

IgG in colostrum is important for

Answer 36

systemic protection of the neonate

Question 37

IgA in milk is important for

Answer 37

mucosal protection of the neonate

Question 38

Absorption of colostrum

Answer 38

- Colostrum IgG binds to specialised Fc receptors expressed on intestinal epithelial cells of neonates (FcRn). - Antibodies are actively taken up and passed into lacteals and then on to blood.

Question 39

Absorption of colostrum : how long is this process active?

Answer 39

This process is only active for the first 24 hrs after birth (most absorption in first 6-12 hrs)

Question 40

Maternally-derived antibodies (MDA) provide protection for how long?

Answer 40

~12 weeks. Can interfere with vaccination

Question 41

Antibodies in milk;

Answer 41

- No longer any systemic absorption of antibodies - But milk contains IgA which continues to protect the GIT of the neonate from enteric pathogens

Question 42

Failure of Passive Transfer (FPT) =

Answer 42

Insufficient or poor quality colostrum produced by mother – Premature birth – Nutritional deficiencies Inadequate intake by newborn

Question 43

Why is FPT a major concern in foals

Answer 43

- Foals need at least 400 mg/dL serum IgG - Foals are susceptible to infection

Question 44

Diagnosis of FPT:

Answer 44

Blood test ~12 hours of age

Question 45

Treatment of FPT

Answer 45

If tested < 400 mg/dL and foal less than 18 hours old – Administer oral colostrum to ‘top up’ If tested < 200 mg/dL and foal more than 18 hours old – Can administer IV plasma infusion

Question 46

Neonatal isoerythrolysis:

Answer 46

Stallion and mare have incompatible blood types: - Foal inherits sire’s RBC antigens - Mare makes antibodies to foetal RBCs - Foal is born and suckles, absorbing IgG into the circulation - Maternal antibodies attack foals RBC’s - Anaemia and jaundice result