Hypersensitivity

Question 1

What is meant by hypersensitivity?

Answer 1

Exaggerated/ inappropriate immune responses

Question 2

What does type 1 hypersensitivity involve?

Answer 2

IgE mediated reactions

IgE secreted usually

Question 3

3 phases of type 1 hypersensitivity

Answer 3

Sensitisation phase
Activation phase
Effector phase

Question 4

What is meant by sensitisation phase?

Answer 4

Exposure to allergens - activate the Th2 cells-stimultae B cells to form IgE plasma cells
IgE produced in response to antigenic stimulus and binds to Fc receptors on most cells and basophils

Question 5

What is meant by activation phase?

Answer 5

R-exposure to antigen triggers mast cell and basophils to respond by release of granules

Question 6

What is meant by the effector phase?

Answer 6

Complex response occurs as a result of histamine and other pharamcologicallt acitve agents releasednby mast cells and basophils

Question 7

Test for type 1 hypersenstivity reaction

Answer 7

Wheat and flare response

RAST-serum sample

Question 8

GI physiological effects of mast cell degranulation

Answer 8

Increase in fluid secretion
increase in peristalsis
can lead to expulsion of GI tract contents

Question 9

ENT physiological effects of mast cell degranulation

Answer 9

Decreased diameter of airways leading to and increase in the amount of mucus
swelling can lead to congestion of the airways

Question 10

Blood vessels physiological effects of mast cell degranulation

Answer 10

Increase in blood flow 
increase in permeability 
increase in lymoh 
increase in fluid 
hypotension than can lead to an anahylatic shock

Question 11

what is meant by atopy?

Answer 11

Localised - reaction targets specific tissues/organs

Question 12

What is the immediate phase in type1 hypersentiivity

Answer 12

IgE mediated mast cell activation

Question 13

What is meant by the late phase in type1 hypersensiitivity

Answer 13

Depending on allergen dose - sustained activation of mast cells

Question 14

What is type 2 hypersensitivity?

Answer 14

antibody mediated destruction of cells

Question 15

What are causes of haemolysis?

Answer 15

Blood transfusions
Haemolytic disease of the newborn
Drug induced haemolytic anaemia

Question 16

How does TII hypersensitvity reactions occur?

Answer 16

Antibody binds to antigen on surface of target cell
Fc receptot on NK cells recognise AB
corss linkage cells target cell leading apoptosis

Question 17

How does TIII hypersensitivity occur?

Answer 17

WHenever immune complexes are deposited

Question 18

What happens during TIII hypersensitivity?

Answer 18

Recruitment of neutrophils to the site and lytic enzymes cause tissue damage

Question 19

examples of TIII hypersensitivity

Answer 19

Farmers lung
Pigeons fancier disease
Serum sickness

Question 20

What is Type IV hypersensitivity?

Answer 20

Localised inflammation produced by Th cells
large influx of inflammatory cells and macrophages
if antigen is not easily phased

Question 21

What are the stages of prolonged Delayed - type hypersensitivity?

Answer 21

Macrophages adhere to each other 
Fuse to form multinucleated giant cells 
Form palpable nodules 
release lytic enzymes 
tissue damage