Hypersensitivty

Question 1

what is hypersensitivity?

Answer 1

exaggerated inappropriate adaptive immune response

Question 2

what is sometimes a result of hypersensitvity?

Answer 2

inflammatory reactions and tissue damage result

Question 3

when does hypersensitivity manifest?

Answer 3

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

Question 4

how many types of hypersensitivity are there?

Answer 4

4 -Type I, II, III and IV

Question 5

what types are antibody mediated?

Answer 5

Types I,II, III

Question 6

what type is mediated by T cells and macrophages?

Answer 6

Type IV

Question 7

what immunoglobulin is involved in Type I hypersensitivity?

Answer 7

IgE

Question 8

what is type I hypersensitivity ?

Answer 8

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

Question 9

what does IgE bind to?

Answer 9

IgE binds to FcRI on mast cells

Question 10

what occurs at the second encounter in type I?

Answer 10

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

Question 11

what inflammatory mediators are released in type I ?

Answer 11

Release of histamine, prostaglandins,

leukotrienes and other mediators of allergic response

Question 12

what are 4 treatments for mild type I hypersensitivity?

Answer 12

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

Question 13

what is an example of a severe type I reaction?

Answer 13

anaphylactic shock

Question 14

what are symptoms of anaphylactic shock?

Answer 14

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

Question 15

how is anaphylactic shock treated?

Answer 15

with adrenaline immediately

Question 16

What is type II hypersensitivity ?

Answer 16

Antibody-dependent cytotoxic hypersensitivity

Question 17

how long after exposure does type II hypersensitivity occur?

Answer 17

occurs in 12-18 hours of exposure to antigen

Question 18

when does type II hypersensitivity occur?

Answer 18

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

Question 19

what is a result of type II?

Answer 19

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

Question 20

Name example of type II reactions.

Answer 20

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

Question 21

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

Answer 21

• 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

Question 22

what caused a reduction in child mortality from haemolytic disease?

Answer 22

Anti-RhD Prophylaxis

Question 23

when does type III hypersensitivity occur?

Answer 23

18-24 hours after exposure

Question 24

what is an example of type III?

Answer 24

extrinsic allergic alveoli’s

Question 25

what is type III hypersensitivity mediated by?

Answer 25

persistence and deposition of | antibody-antigen immune complexes

Question 26

What are immune complexes influenced by?

Answer 26

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

Question 27

what happens when the immune complexes are deposited?

Answer 27

cause severe inflammation

Question 28

when does type IV hypersensitivity occur?

Answer 28

48-72 hours post Ag exposure

Question 29

what are the 3 types of type IV hypersensitivity?

Answer 29

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

Question 30

what is type IV hypersensitivity mediated by?

Answer 30

T cells and macrophages

Question 31

what are the two phases of type IV hypersensitivity?

Answer 31

- sensitisation | - elicitation

Question 32

Describe sensitisation of type IV hypersensitivity.

Answer 32

- Ag encountered by dendritic cell in skin - Migrates to lymph node - Presents Ag to CD4+ T cell

Question 33

Describe elicitation of type IV hypersensitivity.

Answer 33

- Ag subsequently encountered - Memory T cells are triggered - Inflammation

Question 34

what dental materials is type IV hypersensitivity seen to?

Answer 34

- Amalgam alloy - Gold - Mercury - Resin-based materials

Question 35

What is an example of contact type IV?

Answer 35

Eczematous reaction at point of contact with Ag i.e nickel

Question 36

what is an example of tuberculin type IV?

Answer 36

skin swelling develops after intradermal exposure i.e following injection of tuberculin bacilli

Question 37

what is an example of granulomatous type IV?

Answer 37

Granuloma formation - aggregation and | proliferation of macrophages persisting for weeks