10: Hypersensitivity

Question 1

Type I

Answer 1

allergy and anaphylaxis

Question 2

Type II

Answer 2

antibody-mediated cytotoxicity

Question 3

Type III

Answer 3

immune complex disease

Question 4

Type IV

Answer 4

delayed-type hypersensitivity

Question 5

type I, II, III = antibody mediated

Answer 5

type IV = cell-mediated

Question 6

Type I method

Answer 6

antigen binding to surface of IgE-coated basophils or mast cells

Question 7

atopic = increased tendency to develop allergies

method?

Answer 7

atopic individuals make IgE to allergens

Question 8

development of anaphylaxis

Answer 8

1. allergen + B cell -> plasma cell producing IgE antibodies
2. IgE binds Fc receptors on basophils and mast cells
3. Subsequent exposure: antigen crosslinks IgE on baso/mast cell leading to activation and degranulation

Question 9

anaphylactic death

Answer 9

smooth muscle contraction and edema

Lungs: death bc passages narrow and fill with fluid

Question 10

Histamine effect

Answer 10

bronchial smooth muscle contraction and increased vascular permeability

Question 11

Proteases effect

Answer 11

activate matrix metalloproteinases –> cleave tissue matrix proteins and cause damage

Question 12

TNFalpha

Answer 12

promotes inflammation

Question 13

Eosinophil chemotactic factor

Answer 13

accumulates at site of ‘injury’ and attempts to counteract the effects of histamine

Question 14

LTC4 LTD4 and LTE4

Answer 14

leukotrienes

similar effects as histamine, but must be synthesized so it is a sustained, delayed effect

Question 15

epinephrine because it relaxes smooth muscle is only reversal of anaphylaxis

Answer 15

antihistamines: block binding of histamine

cromolyn sodium and theopylline: block degranulation

Question 16

type II antibody mediated method

Answer 16

antibody binds directly to tissue and…

1) destroys tissue (cytotoxicity)
2) interupts normal cellular function

Question 17

examples of type II antibody mediated hypersensitivity

Answer 17

hemolytic disease of the newborn
grave’s disease
myasthenia gravis

Question 18

Pathogenesis of type III hypersensitivity

Answer 18

• immune complexes lodge in tissues and cause complement activation
• C5a leads to neutrophil accumulation
• lysosomal enzymes in neutrophil damage the tissue

Question 19

serum sickness

Answer 19

caused by repeat injection of foreign serum (anti-venoms are a good example)

Question 20

how are immune complexes normally removed?

Answer 20

• RBCs have CR1 protein that binds C3b and C4b on immune complexes
• take the immune complex to liver and spleen where they are removed from blood by macrophages

*in type III this is overwhelmed

Question 21

delayed-type IV

Answer 21

days after exposure to antigen
requires memory just like all the other ones
may form granuloma or contact dermatitis
Tb skin test