Allergies

Question 1

What is a type 1 hypersensitivity? eg.?

Answer 1

IgE mediated immediate hypersensitivity

eg. skin allergy like sweet itch - Midge bite hypersensitivity

Question 2

What is the difference between an immune response and an allergic response? Give examples of both.

Answer 2

Both very similar, both involve IgE
Sarcoptic mange evokes an immune response whereas cat fleas evoke an allergic response
Allergy is unregulated and an inappropriate immune response - mimics a parasite response but it is not limited to the stimulus

Question 3

When is IgD produced?

Answer 3

Very beginning of the immune response.. stops shortly after starting

Question 4

What is IgG good for?

Answer 4

Bacterial infection - Complement, opsonisation

Question 5

How are T cells involved in the humoral response?

Answer 5

Help B cells switch antibody class

eg. TH2, releasing IL4, IL5, IL13 -> IgE, IgG and IgA stimulated
- Whereas TH1, releasing IFNy and TH17, releasing IL17 -> IgG only

Question 6

What causes T helper cells to differentiate?

Answer 6

Antigen presenting cells providing signals 
eg. 
IL12 -> TH1 
IL4 -> TH2 
IL6+TGFb -> TH17
Vit A (Retinoic acid) + TGFb -> T-reg

Question 7

Which cells down regulate the IgE/IgG/IgA response?

Answer 7

T-reg, IL10, TGFb, IFNy

Question 8

What does TGFb stand for?

Answer 8

Transforming Growth Factor B

Question 9

What tells APCs which cytokines to produce?

Answer 9

PAMPs, DAMPs, NLRs, TLRs, non infectious mediators of inflammation

Question 10

Give 4 factors that influence allergy

Answer 10

Metabolic effects eg. very active people -> ^risk of ME
Hormonal effects eg. can grow out of an allergy, pregnancy can v allergies
Hypoxia eg. localised ischeamia (stroke/cardiac infarction)
NTs - ^ risk of depression -> ^ risk of ME

Question 11

What is ME?

Answer 11

Myalgic Encephalomyelitis

- chronic fatigue syndrome

Question 12

Are IgE levels in the blood normally high or low? Where is IgE found?

Answer 12

LOW in blood
Binds to FcE receptors on basophils (=mast cells) and primes them for detection of pathogens
Also found on monocytes and DCs

Question 13

What is the usual half life of Igs?

Answer 13

Weeks/Months

Question 14

What may be found histologically in allergic skin disease?

Answer 14

Accumulation of IgE

Question 15

Where are mast cells found?

Answer 15

Mucosal surfaces and connective tissue

Question 16

Where may IgE be found other than mast cells?

Answer 16

Monocytes and dendritic cells

Question 17

What occurs when a mast cell encounters a parasite?

Answer 17

IgE crosslinked -> Mast cell degranulation
- Pro-inflammaotry substances eg. 
> Histamine
> LTs 
> IL4, IL5, TNFa
> Eosinophil chemotactic factor 
> Proteases

Question 18

Which cells do mast cells attract and activate?

Answer 18

Eosinophils
- Once activated these too will express IgE receptors and degranulate
> IL3, IL5, IL8, LTs, PAF
> Peroxidase (toxic to cells, parasites, -> histamine release from mast cells)
> Collagenase (Remodells connective tissue matrix)
> Major Basic Protein and Eosinophil Cationic Protein (Toxic to tissue cells, nerves, parasites, also -> histamine release from mast cells)

Question 19

Outline the lifecycle of A. Perfoliata

Answer 19

Immature A. Perfoliata taken into Oribatid mite in AUTUMN, overwinters in this IH.
Horse consumes mite.
Immature A. Perfoliata attaches at Ileoceacal Junction
Matures - Gravid proglottids release eggs.
Eggs released in faeces.

Question 20

What is the full name of A. Perfoliata? What is the name of the Intermediate Host?

Answer 20

Anoplacephala Perfoliata (cestode)
- Oribatid Mite

Question 21

When are young A. Perfoliata numbers in pasture high? When are they low?

Answer 21

Autumn

Low numbers at end of summer

Question 22

What type of feeder is A. Perfoliata?

Answer 22

Unarmed - plug feeder

Question 23

What pathological changes are seen at the site of attachment?

Answer 23

Gross thickening and fibrosis 
Erosion of epithelium 
Acute inflammatory response (IL1, IL6) 
Inflitration of leucocytes, mast cells, eosinophils 
Sub-mucosal oedema fibrosis (?)
^ Mucous secretion

Question 24

Are A. Perfoliata eggs easy to detect?

Answer 24

NO

Question 25

What pathological changes are seen in chronic infection?

Answer 25

Tissue adjacent to site of attachment 
- Hyperplasia of epithelium 
- ^ goblet cells 
- ^ easinophils 
- Hyperplasia of muscle 
- Modest oedema of sub-mucosa 
- Gut motility affected -> COLIC 
(blockage or ileoceacal prolapse)

Question 26

How may A. Perfoliata cause colic?

Answer 26

Blockage or ileoceacal prolapse

Question 27

Which ILs are anti parasitic?

Answer 27

IL13, IL4 (TH2 cytokines)

Question 28

Which cytokines down regulate the immune response?

Answer 28

IL10, TGFb

Question 29

How may parasites modulate the immune system?

Answer 29

Upregulate Tregs which in turn down regulates TH2s, meaning they are safe!

Question 30

What does complex regulation of immune responses prevent?

Answer 30

Risk of autoimmunity, hypersensitivity and excessive tissue damage