Type I Hypersensitivity

Question 1

Type I hypersensitivity is also called

Answer 1

Immediate hypersensitivity

Question 2

Define immediate hypersensitivity

Answer 2

Is a type of pathologic reaction that is caused by release of mediators from mast cells

Question 3

What immune cell is involved in type I hypersensitivity

Answer 3

Mast cells

Question 4

Type I hypersensitivity is often triggered by what immunoglobulin

Answer 4

IgE Immunoglobulin E

Question 5

List the two ways antibodies cause diseases

Answer 5

1. Antibody mediated (type II)
2. Immune complex diseases type III( antibodies against soluble antigens)
3. T-cell mediated diseases

Question 6

In many human immunologic diseases, the damage results from the combination of

Answer 6

Antibody mediated and T-cell mediated diseases

Question 7

Immediate hypersensitivity causes

Answer 7

Rapid vascular leakage
Mucosal secretion
Followed by inflammation

Question 8

IgE mediated immediate hypersensitivity reaction are also called

Answer 8

Allergy or Atopy

Question 9

Sequence events I the development of type I hypersensitivity begins with (6 steps)

Answer 9

1. Activation of T-helper 2 cells
2. Production of IgE antibodies in response to antigen
3. Binding of the IgE to Fc receptor cells
4. Exposure to antigens
5. Cross linking of the bound IgE by the antigen
6. Release of mast cell mediators

Question 10

Functions of mast cells in type I hypersensitivity

Answer 10

1. Rapid increase in vascular permeability
2. Smooth muscle contraction

Question 11

What mast cell mediators recruit neutrophils and eosinophils to site of reaction

Answer 11

Cytokines

Question 12

What inflammatory component is responsible for tissue injury that results from repeated immediate hypersensitivity

Answer 12

Late-phase reaction

Question 13

List the mediators found in type I hypersensitivity

Answer 13

Vasoactive amines
Lipid mediators

Question 14

What 2 cytokines are secreted by T-helper 2

Answer 14

Interleukin -4 (IL-4)
Interleukin -3 (IL-3)

Question 15

What are the functions of IL-4 and IL-3

Answer 15

Stimulate B lymphocytes specific for the foreign antigens to switch to IgE producing plasma cells

Question 16

IgE antibody produced in response to an allergen binds to high affinity Fc receptor,specific the Fc chain involved and why

Answer 16

€ heavy chain because they are expressed on mast cells

Question 17

What term describes the coating of mast cells with IgE

Answer 17

Sensitization

Question 18

Where are mast cells located

Answer 18

1. In all connective tissues
2. Adjacent to blood vessels
3. Under epithelial tissues

Question 19

Which of the body’s mast cells are activated by cross linking of allergen specific IgE often depends on

Answer 19

Route of entry of the allergen

Question 20

The high affinity receptor for IgE called

Answer 20

Fc €RI ( IgE Fc receptor)

Question 21

Fc€RI consits of 3 polypeptide chains namely

Answer 21

1. One binds the FC portion to the € heavy chain very strongly with a Kd of approximately 10^-11
2. Other 2 chains of the receptor are signaling proteins

Question 22

Where else is Fc€RI present

Answer 22

Basophils (circulating cells with many features of mast cells)

Question 23

Mast cell activation results from

Answer 23

Binding of 2 or more IgE antibodies on the cell

Question 24

Activation of mast cells trigger biochemical signals from transducing chains of Fc€RI. The signals lead to 3 responses in the mast cells;

Answer 24

1. Degranulation (rapid release of granule content)
2. Synthesis and Secretion of Lipid mediators
3. Synthesis and Secretion of Cytokines

Question 25

Mention the most important mediators released by mast cells

Answer 25

1. Vasoactive Amines and Protease stored in and released from granules 2. Arachidonic acid metabolism and Cytokines

Question 26

Mention the major amine produed

Answer 26

Histamine

Question 27

What are the functions of histamine

Answer 27

1. Causes dilation of small blood vessels 2. Increases vascular permeability 3. Stimulates the transient contraction of smooth muscles

Question 28

The function of protease is

Answer 28

Causes damage to local tissues

Question 29

Mention 2 contents of arachidonic acid metabolism

Answer 29

Prostaglandins Leukotrienes

Question 30

Function of prostaglandins

Answer 30

Causes vascular dilation

Question 31

Function of leukotrienes

Answer 31

Stimulate prolonged smooth muscle contraction

Question 32

Function of Cytokines

Answer 32

Induce inflammation (late phase reaction)

Question 33

What cytokines causes the late phase reaction

Answer 33

Leukocytes

Question 34

List the leukocytes involved in late phase reaction

Answer 34

Eosinophils Neutrophils T-helper 2 cells

Question 35

What promote neutrophil and eosinophil rich inflammation

Answer 35

Tumor necrosis factor (TNF) IL-4

Question 36

What contributes to leukotrienes recruitment

Answer 36

Chemokines produced by mast cells Chemokines produced by epithelial cells