Hypersensitivity Flashcards
Define hypersensitivity
An abnormal or exaggerated reaction to the ingestion, inflation or contact with a substance that does not provoke such a reaction in most people
What is an allergic reaction?
A hypersensitivity reaction to a normally innocuous substance that is mediated by the immune system
What can a person with mercury allergy experience
Burning mouth syndrome
List the different classifications of hypersensitivity reactions
Type I
Type II
Type III
Type IV
What are hypersensitivity reactions grouped according to?
- The Immune effector mechanisms that mediate the response e
- The type of antigen that stimulates them
What are type I hypersensitivity reactions mediated by?
IgE and mast cells
Before having a type I hypersensitivity reaction what must an individual be?
Must be sensitised
What is the antigen associated with type I hypersensitivity reactions?
Any soluble antigen
Talk through the steps of a type I hypersensitivity reaction
- Soluble antigen is picked up by dendritic cells
- Dendritic cell primes immune response, plasma cells migrate to mucosa and release allergen specific IgE
- IgE binds to mast cells via the Fc region of the antibody binding to Fc receptors on mast cells
- Following re exposure allergic binds to and clusters the IgE on the mast cell
- This signals the FcR triggering mast cell degranulation releasing histamine
What is the overall effect of a type I hypersensitivity reaction?
Mast cell activation, degranulation and the release of histamine
Give some examples hypersensitivity reactions
- Allergic reactions
- Allergic asthma a
- Atopic eczema
- Anaphylaxis
- Some drug allergies
What is another name for type IV hypersensitivity reactions
Delayed type hypersensitivity reactions
What is type IV hypersensitivity mediated by?
T cells
Name the different T cells that can cause type IV hypersensitivity ?
Th1
Th2
Cytotoxic T cells
What is the antigen associated with type IV hypersensitivity reactions?
Soluble antigen
What are allergens?
Small and highly reactive molecules that bind to and immunologically alter host proteins
What are the two stages of a type IV hypersensitivity reactions
Sensitisation
Elicitation
Give examples of type IV hypersensitivity reactions that are mediated by Th1
Allergic contact Dermatitis
Tuberculin reaction
Give examples of type IV hypersensitivity reactions that are mediated by Th2 cells
Chronic astma
Chronic allergic rhinitis
Give examples of type IV hypersensitivity reactions that are mediated by Cytotoxic T cells
Graft rejection
Allergic contact dermatitis to poison ivy
What is the effect of a type IV hypersensitivity reaction mediated by Th1 cells
Macrophage activation
What is the effect of a type IV hypersensitivity reaction mediated by Th2 cells
IgE production
Esinophil activation
Mastocytosis
What is the effect of a type IV hypersensitivity reaction mediated by cytotoxic T cells
Cytotoxicity
Name three dental allergens
- Latex
- Antibiotics
- Dental materials/ metals
What is the most common problems associated with latex
- Contact dermatitis and delayed type IV hypersensitivity
2. Type 1 IgE mediated response (More serious)
What are some of the symptoms of a latex allergy?
- Mild irritation of mucosa
- bronchospasm,
- airway oedema
- vasodilation resulting in hypotension.
When can a type IV latex allergy start to show symptoms and list some of the symptoms
Symptoms can start to show 24+ hours after contact
Symptoms include: erythema, pruitis, eczema and vesicles
When can a type I latex allergy start to show symptoms and list some of the symptoms
Symptoms can start to show mins- hours after contact
Symptoms include: erythema, pruitis, eczema, bronchospasm, vomiting, vasodilation, hypotension and death
What is the frequency of penicillin allergy in dental patients
1 in 10 frequency
What type of hypersensitivity reaction can antibiotic allergy cause?
Type II
cutaneous, non-IgE mediated rash
What can some antibiotic allergies lead to
- cutaneous, non-IgE mediated rash
- Loss of red blood cells or neutrophils.
- hives or possible anaphylaxis.
After placing amalgam restorations what has been seen in a small proportion of patients
Delayed hypersensitivity reactions such as lesions with erythema and pruritic (itch) on the oral mucosa and oral lichen planus
What is burning mouth syndrome an allergic reaction to?
Mercury
List some metals people may be allergic to
- Mercury
- Nickel
- Chromium
- titanium
List some clinical manifestations of nickel allergy
- gingival hyperplasia,
- numbness
- burning sensations.
In whom is a titanium allergy common in?
patients with pacemakers
