Hypersensitivity/allergy L4

Question 1

What are the 3 cayses of hypersensitivity

Answer 1

Allergy, reactions to infections, autoimmune diseases

Question 2

What are type 1,2,3 from

Answer 2

Antibody mediated, sometimes via th2 response

Question 3

What is thpe 4 mediated by

Answer 3

Delayed t cell responses , 17,1,cd8

Question 4

What hppens on first exposure in type 1

Answer 4

Pamp from allergens like pollen in hay fever can cause actication of apc like dc and macrophages. Apc allows th2 differentiation. Th2 then via TD responses binds b cells via cd40, secretion of il4,il13 can cause class switching to ige, mast,baso and eosinophil attraction too

Ige then binds fcr e on the mast or basophils causing it to be sensitised for secondary exposure

Question 5

Which cytokines from th2 ade important in th2 ewsponse and ige response in type 1 hypersensitivity

Answer 5

Il4,13 and 5 for eosinophil production

Question 6

What are mast or basophils exposed to ige on fiest exposure

Answer 6

Sensitised for secondary eg pollen again

Question 7

What happens on secondary exposure

Answer 7

Instanr degranulation of things like tnf a, histamine

Lipid production of things like pgd2

All cause inflammation eg in airway

Question 8

Where are type 1 allergens usually found and give examples

Answer 8

Mucosal surfaces

Wg food, pollen, drugs

Question 9

What types of genetic polymorphisms can affect hypersensitivity type 1

Answer 9

Mhc, il 4, fcr e on mast and basophils

Question 10

Which ab are made against alletgens in type 2 which mediate hypersensitivity

Answer 10

Igg and igm

Question 11

Where are allergens in type 2 found

Answer 11

Cell bound eg rh on rbc

Question 12

How does complement have a part in type 2

Answer 12

Gets actucated by igg and igm via c1q, produces opsin coating the cell with allergen on it for phagocytosis.
Also mac which kills the cells too

Question 13

What other yype of ab mediated killing in type 2 to innocent cells

Answer 13

Adcc via fcr on cells like eosinophils and nk cells which then kill the cells cia granules

Question 14

What are frustrated phagocytes and how does this cause tissue damage in type 2

Answer 14

When they try engulf the complement or ab coated cells with allergens on them via fcr or c3b recetors. Too larhe fells cause release of lysosomal products = tissue dmaage

Question 15

Explain haemolytic disease of newborn as a type 2 example

Answer 15

If a chuld has rh ag on their rbc and mother is nevstice. She makes anti rh in her first pregnancy. Usually igg. On second pregnancy, anti rh will cross placenta and fix complement and themselebs on rbc causing the killing of rbc = anemia

Question 16

What causes brain damage in haemolytic disease

Answer 16

Hg breakdown into billirubin

Question 17

What treatment is used for haemolytic disease

Answer 17

Uv to interfere with billirubin

Ab which bund rbc wne block anti rh

Question 18

How can drugs inruce haemolytic diaease

Answer 18

Can bind rh which then attract ab for the frugs

Question 19

Ehat is responsible for type III eg RA

Answer 19

Igg complex with soluble allergens to form immune complexes (ICs)

Question 20

What happens to ICs not cleared

Answer 20

Deposited on tissue causig damage, inflammation and blockage wg of kidney

Question 21

Which size ICs are good and why

Answer 21

Large ic can be removed by complement activation wnd therefore c3b qnd mac mediated removal

Question 22

What do small ic bind to which causes mast cell degranulation causing problems

Answer 22

Fcr y on mast or basophils

Question 23

What happens when small ics bind to neutrophils via fcr y

Answer 23

Cant be phagocytosed well. Causes rekease of lysosomal content for tissue damage

Question 24

What happens if the small ic bind macrophages

Answer 24

Macrophage pahgocytosis releases inflammatory cytokines and other mediators of inflammation

Question 25

What determines site of immunopathology eg skin, kidney, joints

Answer 25

Where allergen is deposited eg via iv, subcutaneous, inhalation

Question 26

What happens in thpe 4 on first exposure

Answer 26

Allergen taken up by apc which then travel to lymph and cause differentiation eg into th1 response or cd8 if mhc1.

Question 27

What happens on reexposure

Answer 27

Memroy t cells instantly release cytokines like ifny, il2 which acticates macrophages sexreting inflammatory like tnfa,il8,gm-csf

Question 28

Dermatitis of rhe skin can be caused by metals like nickel. How

Answer 28

Taken in by skin barrier if disrupted. Causes peptide modification. The modified perise prwsented on cells like langerhans skin cells Move to lymph to activate th1 differentiation Acticate macrophages can secrete inflammatory cytokines like tnf a

Question 29

What allergen example allows cd8 reapinse in type 4

Answer 29

Urushiol oil in poison ivy which modifies peptides

Question 30

Explain the poison ivy xausing blisters

Answer 30

Langerhans can present on mhc II so cd8 kill the cells eg via granzymes. This causes blistering of the skin

Question 31

What is the hygiene hypothesis

Answer 31

Causes lack or inbalance between th1 and th2 responses because lack of pathogen exposure increasint sensutivrt to allergens

Question 32

How can environment impact allergy predisposition

Answer 32

Cigarettes, air pollution, microbiota changes, low fibre diets can all allow type 1 responses and also type 4 if epi barrier disrupted for dermatitis

Question 33

How does th2 affect airway

Answer 33

Inflammation and collagen build up refuces lumen space eg in asthma

Question 34

What is the most prevalent hypersensitivity for atopic allergy

Answer 34

Type 1 ige th2

Question 35

How does type 1 allow early pahse of asthma

Answer 35

Reaction to allergens causes mast cell effects like bronchoconstriction eg via ltc4, mucus building, vasodilation etc via eg histamine

Question 36

How can ige in gi tract be an issue

Answer 36

Causes comiting and diarrhoea by histamine h1 causing broncho and smooth muscle constriction

Question 37

Does histamine increase mucus

Answer 37

Yes

Question 38

What are allergy treatments

Answer 38

Antihistamine Epinephrine if anaphylaxis to relax airways Bronchodilators

Question 39

How does desensitatuon cia immunitherapy work

Answer 39

Allergen ticen in small doses to reduce ige respinses and allow igg4 class switching instead which blocks binding to fcr e

Question 40

Name a biological therapy for atopic allergies

Answer 40

Ma which block ige cross linking via binding fc on ige to stop fcr e binding on mast/baso