Oral mucosa: Allergies Flashcards
Define allergy
When immune system responds in an exaggerated or inappropriate way to an extrinsic (non-self) antigen
Define autoimmunity
When immune system responds in an exaggerated or inappropriate way to an intrinsic (self) antigen
Define hypersensitivity
When immune system responds in an exaggerated or inappropriate way resulting in harm
e.g. allergy and autoimmunity are forms of hypersensitivity
When does hypersensitivity occur?
Occurs on 2nd exposure to antigen
Is a characteristic of the individ (genetics involved)
Types of hypersensitivity?
Type I - immediate/anaphylaxis
II - cytotoxic
III - immune complex
IV - delayed
How is type IV hypersensitivity mediated?
Cell mediated
What hypersensitivities are antibody mediated?
I, II, III
Type I hypersensitivity features?
Anaphylaxis Rapid onset IgE mediated Antigen gives rise to type I hypersensitivity rxns Most allergens are small proteins
What does histamine release in type I hypersensitivity cause?
Vascular dilation (vasodilation)
Increased vascular permeability e.g. oedema
Bronchospasm
Urticarial rash
Increased nasal and lacrimal secretions = runny nose
What do type I hypersensitivity reactions most commonly present as?
Hayfever
Asthma
Acute allergic rxns
Angio-oedema/anaphylaxis e.g. penicillin, latex allergies
How to diagnose type I hypersensitivities?
Wheel and flare skin test
Apply small amount of allergen under skin using prick test
Wheel caused by extravasation of serum into skin due to histamine e.g. angio-oedema
Flare caused by axon reflex
Late phase 6hrs plus due to leukocyte infiltrate and more oedema
How to manage type I hypersensitivities?
Adrenaline
Antihistamines
Corticosteroids
Avoidance of allergen
Type II hypersensitivity features?
Antibodies target self antigens (auto-antibodies)
Usually IgG or IgM
Antibodies induce cell damage and inflammation
Auto-antibodies activate either Antibody dependent cell cytotoxicity (ADCC) OR complement
What does complement activation in type II hypersensitivity result in?
Inflammation Cell death (membrane attack complex)
What are type II hypersensitivity responses important in?
Acute transplant rejection
Autoimmune diseases
- Pemphigus
- Pemphigoid
Type III hypersensitivity features?
Immune complex forms between antibodies and antigens
What can immune complexes in type III hypersensitivity deposit in?
The lining of BVs
Glomeruli
Lung
What can immune complexes in type III hypersensitivity induce?
Complement activation
Neutrophil binding
= Inflammation and vascular permeability
What are type III hypersensitivity reactions important in?
Immune complex mediated vasculitis e.g. erythema multiforme, systemic lupus erythematosus (SLE)
Type IV hypersensitivity features?
Cell mediated - generally localised
Mediated by T cells
Slow to develop, resolve
Localised
Type IV hypersensitivity - what are they important in?
Delayed hypersensitivity responses
Contact dermatitis
Lichenoid reactions to amalgam fillings
Oral lichen planus
How does type IV hypersensitivity occur?
Langerhan’s cells form a network within the epithelium
They intercept and process antigen entering the mucosa
The antigen stimulates keratinocytes to release TNF
= Stimulates langerhan’s cells to migrate to the draining lymph nodes
Langerhan’s cells process than antigen
And present parts of it to T cells circulating though the lymph node
Antigen specific T cells become activated
Proliferate of antigen specific T cells (clonal expansion)
Cytotoxic T cells (CD8) kill basal karatinocytes (apoptosis)
How do T cells kill keratinocytes?
They induce apoptosis by:
Fas/fas-ligand mediated apoptosis
Perforin/granzyme B
What is increasing in the population?
Large increase in children with asthma
and allergic responses in adults
= allergies increasing in dental surgery - latex and dental materials
What are the main concerns regarding allergies in dental surgeries?
Drug allergies
Dental material and latex allergies
Type I reactions - penicillin and other antibiotics, LA, NSAIDs
What can penicillin hypersensitivity reactions cause?
Skin rash
Angioedema
LA allergy?
Rare since preservatives removed from cartridges
Most reactions are vasovagal and due to IV injection
Some rxns due to latex allergies
Allergies in ortho?
Nickel containing wires
Bracket adhesives - bisGMA
Acrylic materials
Allergies in restorative dentistry?
Amalgam
Composite filling materials - bisGMA
Denture bases - acrylics
Rarely metals in crowns and denture bases
How are dental materials grouped?
Into plastics (denture bases and composites) and metals
Usually present as type IV responses
- Usually chronic and localised
- Skin patch testing can be helpful
How to test for type IV hypersensitivity?
Skin patch testing
Samples applied to skin or back of arm for 72-96 hrs
Denture acrylic hypersensitivity - common allergens?
Polymethyl methacrylate Methyl methacrylate monomer Stabiliser (hydroquinone) Initiator (benzoyl peroxide) Chemicals released during polymerisation (formaldehyde)
Cold cure acrylics - why are they a problem?
More hypersensitivity
Less polymerisation
More free monomer, stabiliser, initiator
Activator
What do composite filling materials contain that may cause hypersensitivity?
Quartz or borosilicate fillers BisGMA Low MW monomers e.g. TEG-DMA or EG-DMA Coupling agents Stabilisers, activators, initiators
What do bonding agents contain?
More resin and less filler than composite filling materials
More likely to cause problems
Metal hypersensitivity in dentistry?
Generally type IV
Nickel - ortho wires
Mercury - lichenoid rxns to amalgam fillings
Causes of rubber related reactions?
Latex protein allergy
Chemical allergy
Powder irritancy
Latex protein allergy (type I reactions) occur with?
Skin contact -
- Urticaria
- Angioedema
- Rarely anaphylaxis
Air dispersal on glove powder particles
- Asthma, cough, weeze, rhinitis, rarely anaphylaxis
Chemical allergy - type IV reactions due to?
Accelerators and antioxidants used during manufacture
Chemicals produced during manufacture
Allergic contact dermatitis
75% of work related glove allergies
How to avoid occupational glove allergy problems?
Use powder free and hypoallergenic latex gloves
Latex free gloves
