Oral Allergies Flashcards
What is allergy?
When immune system reaction in exaggerated or inappropriate response to extrinsic antigen
What is auto-immunity?
When immune system responds in exaggerated or inappropriate way to intrinsic antigen
What is hypersensitivity?
When immune system responds in exaggerated or inappropriate way resulting in harm
Are allergies and autoimmunity types of hypersensitivity?
Yes
What are different forms of hypersensitivity?
Antibody mediated
Cell mediated
What types of hypersensitivity are antibody mediation?
Type 1, 2 and 3
What hypersensivity is cell mediated?
Type IV
What is type I hypersensivity
Immediate/ anaphylaxis
What is type II hypersensitivity?
Cytotoxic
What is type III hypersensivity?
Immune complex
What is type IV hypersensitivity?
Delayed
How is type I hypersensitivity mediated?
IgE
When get symptoms of type I hypersensitivity?
Immediate
What happens in type I hypersensitivty
Allegens causes antigen response causing which causes mast cell degranulations causing histamine and enzyme release
What does release of histamine cause?
Vascular dilation Increased vascular permeability = oedema Bronchospasm Urticarial rash Increased nasal/ lacrimal secretions
Common causes of type I response
Hay fever
Asthma
Allergies: penicillin, laxtex etc
How to diagnosis allergy for type I hypersensitivity?
Wheel and flare
Allergy applied using prick test and skin response is fast
What is wheel and flare?
Wheel - extravasation of serum into skin due to histamine
Flare - erythematous red patch caused axon response
Issue w/ wheel and flare test?
Can get late phase 6hrs after due leukocyte infiltrate and oedema
How manage type I hypersensitivity?
Adrenaline
Anti-histamine
Corticosteroid
Use of corticosteroids in type I management?
Dampen immune response
What happens on first exposure to allergy
Antigen bind to B cell
B cell turn to plasma cell –> ab released
Cytokine environment causes plasma clells to secrete IgE ab
IgE enters blood which rapidly bind to mast recoprtos
IgE displayed on Fc receptors on mast cell
How can IgE be used to see if someone is predisposed to allergic reaction?
They will have high serum levels of IgE
What happens on second exposure to antigen?
Have specific IgE
Antigen cross-link Fc rector on mast cell
Transmit intra-cellular signal causing mast cell degranulation
Histamine released
What is a type II hypersensitivity?
Antibody mediated - antibodies target self-antigens usually IgG or IgM = cell damage and inflammation
Mechanism type II?
Antibodies target self-antigens
Autoantibodies activate T cells/ neutrophils/ macrophages causing inflammation of complement
What does complement activation in type II cause?
Caused inflammation and cells death via MAC
What is MAC
Membrane attack complex
What is mechanism of type III?
Immune complex form between antibodies and antigens
What happens to immune complex formed in type III?
Deposits in lining blood vessel/ lung - causes complement activation and neutrophil binding = inflammatory and vascular permability
Give example of type III hypersensitivity?
Erythema multiforme
SLE - systemic lupus erythematosis
What is type IV hyperseniviity mediated by?
Cell- mediated
Mediated by T cellsq
When is type IV delayed?
Response is cellular - slow to develop and resolve
When see type IV sensitivity
Delayed hypersensitivity responses
Contact dermatitis
Lichenoid reactions
OLP
Mechanism of type IV?
Extrinsic antigen enter oral
Dendritic cells intercept and process antigen
Antigen stimulated Langerhans cells to migrate to draining lymph node
Also stimulate keratinocytes to release TNF
What happens in draining lymph nodes in type IV?
Langerhan cell process antigen and presents to T cell circulating in lymph node
Antigen specific T cell becomes activated - proliferation and re-circulation to oral mucosa
What happens in oral mucosa in type IV?
Epithelial cells activated to secrete TNF
TNF induces VCAM-1 expression on endothelium
Allows T cells to bind VCAM-1
Interaction between T cells and epithelium = cytokine release
Cytotoxic T cells kill basal keratinocytes
What see histology of type IV hypersensitivity?
Dense band T cells in connective tissue
2 mechanism in which T cells induce apoptosis?
Fas-mediated
Peforin/ granzyme B
What is perforin?
Pore forming molecule
Type IV summary?
Langerhan cells move from epidermis to lymph nodes
They present antigen to CD4 T cells
T cells move to mucosa to secrete TNF
Causes expression VCAM1
Secretion pro-inflammatory cytokines which damage tissue
When is tissue damage seen in type IV?
12 hours
3 main issues w/ allergies in dentistry?
Drug allergies
Dental material allergies
Latex allergy
What type of reaction is a drug allergy?
Type I
Are LA allergies common?
Not true allergies - preservative been removed
Most reaction vasovagal due intra-vascular injection
What type of reactions are those to dental materials?
Type IV - response usually chronic and localised
What metals are likely to cause type IV responses?
Nickle
Mercury - lichenoid reaction
Alternative to latex gloves?
Nitrile