Type 1 hypersensitivity

Question 1

What is type 1 hypersensitivity?

Answer 1

IgE dependent allergic hypersensitivity (Anaphylactic)

Question 2

What is type 1 hypersensitivity mediated by?

Answer 2

Mast cells, basophils, IgE and allergens

Question 3

What is an allergen?

Answer 3

Substance that when ingested the immune system recognises as foreign and causes an allergic reaction.

Question 4

What does antigenic mean?

Answer 4

Any substance usually a foreign substance capable of evoking an immune response

Question 5

What is an antigen

Answer 5

Usually a foreign substance, such as a toxin a component of a virus, bacterium, or parasite.

Question 6

What are the products of an immune response?

Answer 6

T-cells

Antibodies

Question 7

What is immunological hypersensitivity?

Answer 7

undesirable reactions produced by the normal immune system, including allergies

Question 8

What is the first step in the immune response?

Answer 8

Sensitisation

Question 9

What is the role of antigen presenting cells?

Answer 9

They stimulate the activation of auto-reactive T or B cells

They process and express the allergens on their cell surface

Question 10

Where are mast cells?

Answer 10

(Tissue-dwelling)

Question 11

What is the importance of mast cells?

Answer 11

They contained pre-formed mediators such as; histamine, heparin and proteases

Question 12

How mast cells activated?

Answer 12

By the cross-linkage of cell bound IgE

By IgE Independent mechanisms

Innate immune mechanisms

Question 13

What stages are mast cells involved in?

Answer 13

Early and late inflammatory events

Question 14

Where are mast cells derived?

Answer 14

From bone marrow

Question 15

What is the role of IL-4 and IL-13?

Answer 15

Promotes Th2 and IgE production

Question 16

What is the first step in the Development of allergic sensitisation?

Answer 16

Detection of the allergen by dendritic antigen presenting cells

Question 17

What happens after an allergen is detected?

Answer 17

The APC interacts with naive T lymphocytes cells by ligation of MHC II molecules on the APC by T cell receptors.

Question 18

What happens in the allergen development once the dendritic cell has interacted with a naive T cell?

Answer 18

In the presence of IL-4 the Naive T-cell switches phenotype to TH2
TH2 reacts with naive B cells in the presence of IL-4 and IL-13

Question 19

What happens after this?

Answer 19

B-cells switch to antibody production of IgE

Question 20

What is an important feature of B-cells and T-cells?

Answer 20

They have immunological memory.

In the presence of the allergen it will cause expansion and production of the allergen specific IgE

Question 21

What is the role of TNF-alpha?

Answer 21

Promotes tissue inflammation

Question 22

What are Basophils?

Answer 22

Type of WBC, that circulate the body

Question 23

What do basophils contain?

Answer 23

Histamine and other pre-formed mediators

Question 24

What is the main role of basophils?

Answer 24

They migrate to sites of allergic inflammation.

Question 25

What is the indication of a low basophil level?

Answer 25

A severe allergic reaction

Question 26

How are basophils activated?

Answer 26

Via pathogen associated molecular patterns.

Question 27

What is the most common inflammatory mediator and what is its role?

Answer 27

Histamine - it triggers vasodilation and increases vascular permeability

Question 28

What is IgE cross-linking and what does it cause?

Answer 28

IgE molecules cross linking leading to intracellular signalling.