Hypersensitivity

Question 1

What is hypersensitivity

Answer 1

A state of altered reactivity in which the body reacts with an immune response to a foreign agent (e.g., an allergen)

Question 2

What is an allergen

Answer 2

An antigen that causes an allergic reaction

Question 3

What is the difference between an allergy and intolerance

Answer 3

Allergy involves the immune system while an intolerance involves the digestive system

Question 4

What are the 4 types of hypersensitivity

Answer 4

IgE mediated
Cytotoxic responses
Immun complex responses
Cell mediated responses

Question 5

What is one example of each type of hypersensitivity

Answer 5

1-IgE CUTANEOU ATOPY

2- Cytotoxic HAEMOLYTIC ANAEMIA

3- Immune complex ARTHUS REACTION

4- Cell mediated TUBERCULOSIS

Question 6

What are haptins

Answer 6

Haptens are small molecules that can be recognized by a specific antibody but cannot elicit an immune response
A hapten must be chemically linked to a protein molecule (carrier) to elicit antibody and/or T-cell responses​

Question 7

What is the most common type of hypersensitivity

Answer 7

type 1

Question 8

What produces IgE antibody

Answer 8

B cells

Question 9

What is IgE usually attached to

Answer 9

Basophils

Question 10

How does IgE produce an allergen response

Answer 10

As the allergens bind to IgE histamine is released from mast cells and basophils

Question 11

What can cause a production of histamine

Answer 11

Anaphylaxis
Hay fever
Hives
Eczema
Allergies

Question 12

How are eosinophils and basophils involved in anti-parasitic immunity

Answer 12

Eosiniophils are parasite eaters
Basophils are involved in allergic reactions

Question 13

How does the immune system react in type 1

Answer 13

T cells recognise foreign antigen and release IL-4 and IL-12 to activate B cells

B cells class switch from producing IgM to IgE after first exposure to allergen​

IgE binds to Fc receptor on mast cells or CD63 on basophils​

IgE recognises allergen and next exposure binds rapidly and causes immediate degranulation of immune cells (elicitation)​

Question 14

What is atopy

Answer 14

Genetic predisposition

Question 15

What are examples of cutaneous atopy

Answer 15

Allergic rhinitis (hay fever) ​

Atopic dermatitis (allergic eczema)​

Asthma (lower respiratory tract)​

Allergic reaction to chlorhexidine

Question 16

What is systemic anaphylaxis

Answer 16

Anaphylactic shock

Question 17

Which hypersensitivity causes anaphylactic shock

Answer 17

Type 1

Question 18

What produces anaphylatoxins

Answer 18

Complement pathway (classical)

Question 19

What are the main effects of anaphylactic shock

Answer 19

Respiratory system (narrowing)
Cardiovascular system

Question 20

What can test for type 1 hypersensitivity

Answer 20

Skin patch test ​
-Wheal and flare reaction ​
-Helps to identify the allergen​

Blood test​
-Measures IgE levels in blood​

Oral challenge​
-Diagnoses food allergy​

Question 21

What drugs can be used to treat type 1

Answer 21

Anti-histamines – histamine receptor antagonist​

Hydrocortisone – block histamine synthesis​

Epinephrine – reverses effects of granules (vasoconstriction, relaxes muscles)

Question 22

What are the possible immunological treatments of type 1

Answer 22

Hypo- or de- sensitisation – injections of allergen​

IgE to IgG production ​

Question 23

What drives type 1 hypersensitivity

Answer 23

histamine and anaphylatoxins ​

Question 24

What happens in type 2 hypersensitivity

Answer 24

Involves activation of complement by antibody (not IgE) binding to an antigen (cell surface auto-antigens or allergens) ​

Cell is lysed by membrane attack complex formation (complement) and antibody dependent cellular cytotoxicity (NK cells or CD8+ T cells)

Question 25

When might a type 2 reaction occur

Answer 25

Transfusion of the wrong blood type

Question 26

What does type 3 hypersensitivity involve

Answer 26

reactions against soluble antigens (or allergens) circulating in blood - activates complement which attracts neutrophils to the site

Antibody-antigen immune complexes are deposited in tissues which leads to immune responses​

Question 27

What causes arthus reaction

Answer 27

Type 3 hypersensitivity
Antibody-antigen complexes are localized in blood vessel walls​

Can arise from injected particles (e.g., booster vaccinations) or from inhaled or ingested allergens (e.g., farmers lung)​

Question 28

What is serum sickness

Answer 28

Systemic form of Arthus reaction ​

Antibody-antigen complexes lodge in many different tissues

Question 29

What is Oral erythema multiforme

Answer 29

Characterized by blistering of oral mucosa​

Deposition of immune complexes (IgM-bound immune complexes) in the oral mucous membrane ​

Viral or drug-related (hypersensitivity)​

Caused by type 3 hypersensitivity

Question 30

What is type 4 hypersensitivity

Answer 30

T cell-mediated hypersensitivity reaction (no antibodies)​

Delayed response (due to recruitment of T cells)​

Localized T cell reaction at site of antigen exposure​

Involves both CD4+ T cells (damage via macrophages) and CD8+ T cells (direct damage of cells – cytotoxicity)

-Cytokines secreted by T helper cells activate macrophages and cytotoxic T cells

Question 31

What are examples of type 4

Answer 31

Contact dermatitis
Tuberculosis - granulomasin lung tissue
Oral disease - Orofacial Granulomatous