Immunology - Hypersensitivity

Question 1

What is a hypersensitivity reaction?

Answer 1

Excessive immune responses that cause damage

Question 2

What are the types of antigen that can be reacted to in hypersensitivity reactions?

Answer 2

Infectious agents
Environmental substances
Self antigens

Question 3

Type I hypersensitivity

Answer 3

Immediate
IgE antibody
Th2 cells

Question 4

Type IV hypersensitivity

Answer 4

Delayed hypersensitivity
T cell mediated
CD4+, CD8+ T cells

Question 5

How is type I hypersensitivity mediated?

Answer 5

through degranulation of mast cells and eosinophils

Effects felt within minutes of exposure

Question 6

What are allergens?

Answer 6

Antigens that trigger allergic reactions?

Question 7

Degranulating cells

Answer 7

Release of mediators that cause allergic symptoms

Question 8

Where are mast cells found?

Answer 8

Reside in many tissues

Question 9

When do mast cells initiate allergic symptoms?

Answer 9

After allergen and IgE interact

Question 10

Clinical syndromes of allergy

Answer 10

Anaphylaxis
Asthma
Rhinitis
Urticaria
Angioedema
Atopic eczema

Question 11

Symptoms of anaphylaxis

Answer 11

Low blood pressure
Angioedema
Airway obstruction

Question 12

Pathophysiology of anaphylaxis

Answer 12

Mast cells produce prostaglandins and leukotrienes through the cyclooxygenase and lipoxygenase pathways
Results in vasodilation and increased vascular permeability
Shift of fluids from the vascular to the extra-vascular space resulting in a fall in vascular tone
Severe drop in blood pressure
IN the skin, mast cells release histamine further contributing to welling and fluid shift

Question 13

Treatment of type I hypersensitivity

Answer 13

β2-adrenergic agonists (asthma)
Epinephrine (lifesaving in anaphylaxis)
Antihistamines (for skin, nose and mucus membrane affected allergies)
Specific receptor antagonists 
Corticosteroids

Question 14

What mediates type II hypersensitivity?

Answer 14

Antibodies - IgG or IgM reacting with the antigen present on the surface of cells

Question 15

What effect does type II hypersensitivity have on cells?

Answer 15

Opsonisation of target cells

Immune mediated haemolysis

Question 16

What type of hypersensitivity reaction can be caused by transfusion reactions?

Answer 16

Type II

Question 17

Which antibody is responsible for type III hypersensitivity?

Answer 17

IgG

Question 18

What is type III hypersensitivity?

Answer 18

Immune complex disease

Question 19

Immune complex disease in the kidney

Answer 19

Nephrotic syndrome with gradual development of renal failure

Nephritis with rapid onset renal failure

Question 20

How does type III hypersensitivity cause damage?

Answer 20

Immune complexes of antigen and antibody form and cause damage at the site of production or circulate and cause damage elsewhere

Question 21

When are delayed hypersensitivity reactions initiated?

Answer 21

When tissue macrophages recognize danger signals and initiate an inflammatory response

Question 22

Which cells loaded with antigen migrate to local lymph nodes, where they present antigen to T cells?

Answer 22

Dendritic cells

Question 23

Which factor secreted by both macrophages and T cells stimulates much of the damage in delayed hypersensitivity?

Answer 23

Tumour necrosis factor

Question 24

Treatment of delayed hypersensitivity

Answer 24

Prevention through avoiding antigens
Anti-inflammatory drugs
Immunosuppressive drugs