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.

Question 2

What as allergen?

Answer 2

An antigen that causes an allergic reaction

Question 3

What is Gell and Coombs’s system?

Answer 3

A classification system defines four types of hypersensitivity

Question 4

What are the differences between allergens and haptens?

Answer 4

-Allergens tend to be proteins and have
the ability to elicit an immune response

-Haptens are small molecules (non-proteins) that can be recognized by a specific antibody
but cannot elicit an immune response without chemically linked to a protein molecule (carrier) to elicit antibody and/or T-cell responses

Question 5

What are the most common type of hypersensitivity ?

Answer 5

Type I hypersensitivity

Question 6

By what type I hypersensitivity mediated?

Answer 6

Mediated by the IgE antibody produced by B cells

Question 7

What happen when allergen binds to IgE antibodies?

Answer 7

IgE cross-linking induced deregulation. Causes include anaphylaxis, hay fever, hives,eczema, allergies to certain food.

Question 8

Where do IgE antibodies bind?

Answer 8

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

Question 9

What cells produce IgE antibodies?

Answer 9

B cells

Question 10

What is Atopy cutaneous?

Answer 10

It is a genetic predisposition localized allergic reaction.
Allergic rhinitis (hay fever)
Atopic dermatitis (allergic eczema)
Asthma (lower respiratory tract)
Allergic reaction to chlorhexidin

Question 11

What is systemic anaphylaxis

Answer 11

Anaphylactic shock throughout body, arises from mast cell degranulation

Question 12

Allergy testin

Answer 12

• Skin Patch test
• Blood test - IgE levels in blood
• Food challenge - Identifies food allergy

Question 13

Hoe they treat allergy?

Answer 13

-Drugs:
Anti-histamines – histamine receptor antagonist.
Hydrocortisone – block histamine synthesis
Epinephrine – reverses effects of granules
(vasoconstriction, relaxes muscle

-Immunological treatment:
Hypo- or de- sensitisation – injections of allergen
IgE to IgG production

Question 14

How cells can be destroyed in Type II hypersensitivity?

Answer 14

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

Question 15

Examples of Type II hypersensitivity?

Answer 15

1- transfusion of mismatched blood type
2- autoimmune hemolytic anemia

Question 16

What type of hypersensitivity that involves activation of complement by antibody binding to an antigen (cell surface auto-antigens or allergens) ?

Answer 16

Type II hypersensitivity

Question 17

What type of hypersensitivity that involves reactions against soluble antigens (or allergens) circulating in blood so Antibody-antigen immune complexes are deposited in tissues which leads to immune responses?

Answer 17

Type III hypersensitivity

Question 18

How Antibody-antigen complexes are arisen?

Answer 18

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

Question 19

What is the systemic form of Arthus reaction ?

Answer 19

Serum sickness

Question 20

What this image shows?

Answer 20

Serum sickness

Question 21

What is Oral erythema multiforme (EM) ?

Answer 21

Type III hypersensitivity
Characterized by blistering of oral mucosa by deposition of immune complexes (IgM- bound immune complexes) in the oral mucous membrane

Question 22

By what Type IV hypersensitivity?

Answer 22

T cell-mediated hypersensitivity reaction (no antibodies)

Question 23

Why there is a delay in response in type IV hypersensitivity?

Answer 23

Due recruitment of T cells

Question 24

Mention examples of Type IV hypersensitivity

Answer 24

Contact dermatitis
Tuberculosis – granulomas in lung tissue
Oral diseases – orofacial granulomatous (OFG)

Question 25

What 2 immune cells that involve in Type IV hypersensitivity?

Answer 25

Macrophages
T cells