Hypersensitivity Flashcards
(25 cards)
What is hypersensitivity?
A state of altered reactivity in which the body reacts with an immune response to a foreign agent.
What as allergen?
An antigen that causes an allergic reaction
What is Gell and Coombs’s system?
A classification system defines four types of hypersensitivity
What are the differences between allergens and haptens?
-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
What are the most common type of hypersensitivity ?
Type I hypersensitivity
By what type I hypersensitivity mediated?
Mediated by the IgE antibody produced by B cells
What happen when allergen binds to IgE antibodies?
IgE cross-linking induced deregulation. Causes include anaphylaxis, hay fever, hives,eczema, allergies to certain food.
Where do IgE antibodies bind?
IgE binds to Fc receptor on mast cells or CD63 on basophils
What cells produce IgE antibodies?
B cells
What is Atopy cutaneous?
It is a genetic predisposition localized allergic reaction.
Allergic rhinitis (hay fever)
Atopic dermatitis (allergic eczema)
Asthma (lower respiratory tract)
Allergic reaction to chlorhexidin
What is systemic anaphylaxis
Anaphylactic shock throughout body, arises from mast cell degranulation
Allergy testin
- Skin Patch test
- Blood test - IgE levels in blood
- Food challenge - Identifies food allergy
Hoe they treat allergy?
-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
How cells can be destroyed in Type II hypersensitivity?
by membrane attack complex formation
(complement) and antibody dependent cellular cytotoxicity (NK cells or CD8+ T cells)
Examples of Type II hypersensitivity?
1- transfusion of mismatched blood type
2- autoimmune hemolytic anemia
What type of hypersensitivity that involves activation of complement by antibody binding to an antigen (cell surface auto-antigens or allergens) ?
Type II hypersensitivity
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?
Type III hypersensitivity
How Antibody-antigen complexes are arisen?
From injected particles (e.g., booster vaccinations) or from inhaled or ingested allergens (e.g., farmers lung)
What is the systemic form of Arthus reaction ?
Serum sickness
What this image shows?
Serum sickness
What is Oral erythema multiforme (EM) ?
Type III hypersensitivity
Characterized by blistering of oral mucosa by deposition of immune complexes (IgM- bound immune complexes) in the oral mucous membrane
By what Type IV hypersensitivity?
T cell-mediated hypersensitivity reaction (no antibodies)
Why there is a delay in response in type IV hypersensitivity?
Due recruitment of T cells
Mention examples of Type IV hypersensitivity
Contact dermatitis
Tuberculosis – granulomas in lung tissue
Oral diseases – orofacial granulomatous (OFG)
