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Flashcards in Hypersensitivty Deck (37)
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1

what is hypersensitivity?

exaggerated inappropriate adaptive immune response

2

what is sometimes a result of hypersensitvity?

inflammatory reactions and tissue damage result

3

when does hypersensitivity manifest?

not manifest on 1st contact with Ag usually appears on subsequent contact

4

how many types of hypersensitivity are there?

4 -Type I, II, III and IV

5

what types are antibody mediated?

Types I,II, III

6

what type is mediated by T cells and macrophages?

Type IV

7

what immunoglobulin is involved in Type I hypersensitivity?

IgE

8

what is type I hypersensitivity ?

IgE response to innocuous environmental antigens i.e pollen, house-dust mites, latex, some drugs(local anaesthetics)

9

what does IgE bind to?

IgE binds to FcRI on mast cells

10

what occurs at the second encounter in type I?

Second encounter with allergen triggers release
of inflammatory mediators and produces acute inflammatory reaction within minutes with symptoms such as athasma and rhinitis

11

what inflammatory mediators are released in type I ?

Release of histamine, prostaglandins,
leukotrienes and other mediators of allergic response

12

what are 4 treatments for mild type I hypersensitivity?

1. Avoidance
2. Sodium chrooglycate
3.anti-histamines
4. Desensitisation

13

what is an example of a severe type I reaction?

anaphylactic shock

14

what are symptoms of anaphylactic shock?

wheeze, swelling of face
and laryngopharynx,
nausea, dizziness, fainting,
low blood pressure

15

how is anaphylactic shock treated?

with adrenaline immediately

16

What is type II hypersensitivity ?

Antibody-dependent cytotoxic hypersensitivity

17

how long after exposure does type II hypersensitivity occur?

occurs in 12-18 hours of exposure to antigen

18

when does type II hypersensitivity occur?

when IgG or IgM binds to either a self-antigen or a foreign antigen on cells

19

what is a result of type II?

Phagocytosis, killer cell activity or complement-
mediated lysis (Damage is restricted to particular cells/tissues bearing the antigen)

20

Name example of type II reactions.

1. Blood transfusion reactions when ABO incompatible blood is transferred (fever, nausea,vomiting)
2. Haemolytic disease of the newborn

21

Describe the type II reaction of haemolytic disease of the newborn.

- Results from incompatibility of Rhesus D blood antigens to RhD-negative mother
- RhD-positive RBC from 1st foetus sensitise mother usually at birth
-If subsequent foetus is RhD-positive, anti-Rh IgG produced by mother crosses the placenta and attacks foetus
- RhD-negative mothers infused with anti-RhD IgG
immediately after delivery - eliminates all RhD-positive RBC before immune response occurs

22

what caused a reduction in child mortality from haemolytic disease?

Anti-RhD Prophylaxis

23

when does type III hypersensitivity occur?

18-24 hours after exposure

24

what is an example of type III?

extrinsic allergic alveoli's

25

what is type III hypersensitivity mediated by?

persistence and deposition of
antibody-antigen immune complexes

26

What are immune complexes influenced by?

1. Route of Ag exposure eg poor clearance in lung
2. Dose of Ag
3. Size of IC (larger IC fall out of circulation)
4. Binding of Ag directly to tissues

27

what happens when the immune complexes are deposited?

cause severe inflammation

28

when does type IV hypersensitivity occur?

48-72 hours post Ag exposure

29

what are the 3 types of type IV hypersensitivity?

-contact- 48-72 hours
-tuberculin - 48-72 hours
- granulomatous - 21-28 days

30

what is type IV hypersensitivity mediated by?

T cells and macrophages