10 - Allergy Flashcards
Types of hypersensitivity
Slide 6 of lecture
Type II - cytotoxic rxn: immunopathogensis
IgG/M Ab response against combined self-foreign antigen at cell surface –> complement activation + phagocytosis/ADCC
Type II - cytotoxic rxn: clinical features
Onset = minutes to hours
Cell lysis and necrosis
Type II - cytotoxic rxn: common antigen
Penicillin
Type II - cytotoxic rxn: Associated diseases
Erythroblastosis fetalis
Goodpasture’s nephritis
Type III - immune complex rxn: immunopathology
IgG/M Ab against soluble antigen ==> complex deposition
Type III - immune complex rxn: clinical features
Onset: 3-8 hours
Vasculitis
Type III - immune complex rxn: cause
Serum sickness
Type III - immune complex rxn: associated disease
SLE
Type IV - delayed rxn: immunopathology
Antigen specific T-cell mediated cytotoxicity
Type IV - delayed rxn: clinical features
Delayed onset 48-72 hours
Erythema induration
Type IV - delayed rxn: common antigen
Metal e.g. nickel
Tuberculin rxn
Type IV - delayed rxn: associated disease
Contact dermatitis
Immune responses to parasitic disease inc…
Increased [IgE] - specific to antigen + cross-reactive
Tissue inflammation with eosinophilia&mastocytosis. Also basophil infiltration
Presence of CD4+ T cells secreting: IL4, IL5 and IL13
What is the hygiene hypothesis?
Stimulation by microbes is protective. Epidemiological data shows increase in allergy.
Increased atopy (asthma) after anti-parasitic Rx
Prevention of autoimmunity (Crohn’s) by infections
Pro-biotics in pregnant women
Mechanism - Th1 Th2 deviation
Immune response for allergens:
Antigens that initiate an IgE-mediated response
First encounter results in innate and IgM response
How is IgE made?
B cell stimulated by IL4 + Th2 cell
This B cell proliferates
The pathogen binds to B cell and produces IgE
Type I allergic response process
- Allergen binds to CD4 and IL-4 is released.
- B cells produce memory cells and plasma cell.
- Plasma cell makes IgE
- IgE binds to Fc receptor on sensitised mast cell
- Vasoactive amines are released
IgE mediated allergic response: immunopathogensis
IgE Ab mediated mast cell and basophil degranulation –> release of preformed and de novo synthesised inflammatory mediators
IgE mediated allergic response: clinical features
Fast onset (15-30 mins) Wheal and flare
IgE mediated allergic response: late phase response
Eosinophils
Central role for Th2 T cell
What is the role of the Th2?
Multiple cytokine release
Innate inflammatory response
Drive for Ig production
What is the atopic triad?
Asthma, rhinitis, eczema
What is anaphylaxis?
An acute, potentially life-threatening, IgE mediated systemic hypersensitivity response
What makes a diagnosis of anaphylaxis?
History Specific IgE (>0.35 KuA/L) Skin prick test (>3mm wheal) Intra-dermal test Oral challenge test (gold standard) Basophil activation test Component resolved diagnostics
Symptomatic treatment for anaphylaxis
Antihistamines
Steroids
AD
Can do immunotherapy via sub cut or sublingual
Adverse rxns to food
GI - vomiting, diarrhoea, oral symptoms
Resp - rhinitis, bronchospasm
Cutaneous - urticaria, angioedema
Anaphylaxis
