Allergy and Anaphylaxis Flashcards
What can hypersensitivity lead to?
Tissue Damage
How many types of hypersensitivity are there?
4
What is the mediator of a type 1 hypersensitivity reaction?
IgE
What is the onset of a type 1 hypersensitivity reaction?
Within 1 hour
What is an example of a type 1 hypersensitivity reaction?
Anaphylaxis
What is the mediator of a type 2 hypersensitivity reaction?
IgG or IgM cytotoxic
What is the onset of a type 2 hypersensitivity reaction?
Hours to days
What is an example of a type 2 hypersensitivity reaction?
Haemolytic Anaemia
What is the mediator of a type 3 hypersensitivity reaction?
Immune Complex
What is the onset of a type 3 hypersensitivity reaction?
1-3 weeks
What is an example of a type 3 hypersensitivity reaction?
Serum Sickness SLE
What is the mediator of a type 4 hypersensitivity reaction?
T-Cells
What is the onset of a type 4 hypersensitivity reaction?
Days to weeks
What is an example of a type 4 hypersensitivity reaction?
Rash SJS
What is type 1 hypersensitivity?
Immediate or acute hypersensitivity
What can cause a type 1 hypersensitivity reaction?
Pollen
Cat Fur
Insect Stings
Peanuts
Eggs
What are the 2 stages of a type 1 hypersensitivity reaction?
Sensitisation
Secondary Exposure
What happens during the sensitisation stage of a type 1 hypersensitivity reaction?
Antigen Presenting Cell –> CD4 (TH2) –> B Cells (specific IgE antibodies)
Mast cells and basophils.
What happens during the secondary exposure phase of a type 1 hypersensitivity reaction?
Allergen binds to Ab and crosslinks on mast cell and basophil surface
Mast cells and basophils release histamine and other inflammatory mediators
This leads to an inflammatory response
What local or systemic effects do secondary exposures to type 1 hypersensitivity have?
Anaphylaxis or anaphylactic shock - epinephrine
Where is histamine produced?
Mast Cells
Basophils
Enterochromaffin-like Cells
Neurons
Where is histamine found?
Lungs
Skin
GI Tract
How does histamine work?
Acts on G Protein Coupled Histamine Receptors
What are the 4 subtypes of histamine receptors and where are they found?
H1: CNS, endothelium and smooth muscle
H2: CNS, cardiac muscle and stomach
H3: CNS (presynaptic), myenteric plexus
H4: basophils, eosinophils and mast cells
What is the physiological effect of histamine on the immune system?
Releases neutrophils from bone marrow (H4)
Mast Cell Chemotaxis (H4)
Role in hypersensitivity type 1 reactions (H1)
What are the physiological effects of histamine on the cardiovascular system?
Vasodilaton (H1)
Increased cardiac output (H2)
Oedema - increased permeability of post-capillary venules (H1)
What are the physiological effects of histamine on smooth muscle?
Constriction (H1) - ileum, bronchim bronchioles, uterus
What are the physiological effects of histamine in the gut?
Stimulates the secretion of gastric acid, intestinal secretions and increases motility (H2)
What are the physiological effects of histamine on the CNS and PNS?
H2 and H3 are inhibitory (presynaptic)
H1 are excitatory - role in pain and emetic response. Stimulation of sensory nerve endings in the skin results in itching and spread of vasodilation
Signs and Symptoms of Anaphylaxis
Swelling of the conjunctiva
Runny Nose
Swelling of lips, tongue and/or throat
Fast or slow heart rate
Low blood pressure
Hives
Itchiness
Flushing
Lightheadedness
Losss of consciousness
confusion
headache
anxiety
shortness of breath
wheezes or stridor
hoarseness
pain with swallowing
cough
cramps abdominal pain
diarrhoea
vomiting
loss of bladder control
What is a type 2 hypersensitivity reaction?
Antibody dependent cytotoxic hypersensitivity
What are some examples of oral sedating antihistamines?
Chloramphenamine
Clementine
Ketotifen
What are some examples of oral non-sedating antihistamines?
Acrivastine
Bilastine
Cetirizine
Desloratadine
Fexofenadine
Levocetirizine
Loratadine
Mizolastine
Rupatidine
