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53 Cards in this Set
- Front
- Back
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what is an allergy |
hypersensitivity reaction initiated by immunological mechanisms |
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what can hypersensitivity be in response to |
infectious agents, environmental antigens, self-antigens |
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what is the immune reactant in type 1 hypersensitivity reaction |
IgE |
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what is the immune reactant in type 2 hypersensitivity reaction |
IgG |
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what is the immune reactant in type 3 hypersensitivity reaction |
IgG |
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what is the immune reactant in type 4 hypersensitivity reaction |
Th1 cells, Th2 cells, CTL |
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what effector mechanism is activated in Type 1 |
mast cell activation (degranulation of mast cells and eosinophils) |
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what effector mechanism is activated in Type 2 |
FcR+ cells (phagocytes and NK cells) |
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what effector mechanism is activated in type 3 |
FcR+ cells, complement |
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what effector mechanism is activated in type 4 |
macrophage activation, eosinophil activation and cytotoxicity |
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what is an example of hypersensitivity reaction in type 1 |
allergic rhinitis, asthma, systemic anaphylaxis |
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what is an example of hypersensitivity reaction in type 2 |
some drug allergies |
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what is an example of hypersensitivity reaction in type 3 |
serum sickness and arthus reaction |
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what is an example of hypersensitivity reaction in type 4 |
contact dermatitis, tuberculin reaction, chronic asthma, chronic allergic rhinitis |
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what is the first exposure of type 1 hypersensitivity |
sensitisation |
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what is subsequent exposure of type 1 hypersensitivity |
allergen binds to specific IgE on mast cell surface and cross links IgE |
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what are the local symptoms of an allergic reaction |
swelling, itching, nausea, vomiting and diarrhoea |
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what are systemic symptoms of an allergic reaction |
airway obstruction, hives, blood pressure drop and arrhythmia |
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what is an allergen |
an allergen is an antigen that triggers an allergic reaction |
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what are the 2 components of a type 1 response |
early phase and late phase |
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what is the early phase |
starts within minutes of exposure to allergen. It is caused by mediators released by mast cells when IgE is cross linked by allergen. Prostaglandins and leukotrienes are released which increased vascular permeability and vasodilation. |
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what is the late phase |
seen after some hours due to cellular infiltrate (Inflammation) in the tissues |
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describe local reactions |
changes are restricted to site of allergen entry. allergen causes rhinitis, stimulates mast cells in nasal mucosa, vasodil and oedema-nasal stuffiness and sneezing. Leukotrienes also cause increased mucous secretion. |
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what is atopy |
atopy is a tendency to produce IgE in repsonse to low doses of allergens |
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what are atopic diseases |
atopic asthma, allergic rhinoconjunctivitis, atopic dermatitis and IgE-mediated food allergies |
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how much of the population are atopic |
20-30% |
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What can type 4 hypersensitivity also be called |
delayed or cell-mediated hypersensitivity |
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what is type 4 hypersensitivity |
antigen interacts with T cells which releases inflammatory and cytotoxic substances. these attract other whitte blood cells and results in inflammation and tissue injury |
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what is an example of type 4 |
coeliac disease |
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what is anaphylaxis |
potentially life threatening systemic hypersensitivity reaction characterised by being rapid in onset with life threatening airway, breathing or circulatory problems and is usually skin and mucosal changes |
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what causes anaphylaxis |
caused by IgE-mediated immunological release of mediators from mast cells and basophils |
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what is criteria 1 for anaphylaxis |
acute onset of an illness and at least one of; respiratory compromise or reduced BP (or associated symptoms of end-organ dysfunction) |
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what is respiratory compromise |
dyspnoea, wheeze, bronchospasm, stridor, reduced PEF and hypoxaemia |
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what is criteria 2 of hypersensitivity |
two or more of the following; involvement of skin-mucosal tissue, respiratory compromise, reduced BP or associated symptoms, persistent GI symptoms |
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what is criteria 3 of hypersensitivity |
reduced BP after exposure to a known allergen for that patient |
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how do you manage anaphylaxis |
lie patient down or sit up of breathing difficulty, connect to monitors and O2. IM adrenaline. Salbutamol/adrenaline/budesonide nebuliser. IV fluids. IV hydrocortisone and chlorphenamine. Serum tryptase ASAP. admit and observe |
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what are some of the causes of anaphylaxis |
insect bites, latex, food, drugs |
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is insect bite allergy more common in males or females |
males |
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what are the risk factors for death in insect bite allergy |
IHD and chronic lung disease |
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what is the most common insect reaction to |
hymenoptera |
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what are insect sting reactions |
large localised reaction, systemic reaction |
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what does a latex allergy cause |
irritant contact dermititis, allergic contact dermatitis, contact uritcaria, rhinitis, asthma, anaphylaxis |
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what is a type 1 allergy to rubber |
natural latex sap |
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what is a type 4 allergy to rubber |
chemicals used in the manufacturing of latex |
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who is more at risk to latex |
individuals with congenital urinary abnormalities, spina bifida and those who have underdone multiple medical/surgical procedures. Individuals with a history of certain food allergies |
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what can an adverse food reaction be |
immune mediated and non-immune mediated |
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is celiac disease immune mediated or non-immune mediated |
non-IgE mediated |
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what is lactose intolerance |
non-immune mediated metabolic response |
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what are pharmacological non-immune mediated examples |
caffeine, alcohol, salicylates, tyramine, histamine, phenylethylamine |
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what are examples of enzyme deficiencies related to food |
lactose intolerance and favism (G6PD deficiency) |
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what is the big 8 IgE mediated food allergies |
milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, soya |
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what happens in celiac disease with villi |
with celiac disease the villi become inflammed and flattened. This greatly reduces the surface area available for absorption |
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what is IgE mediated food allergy management |
medic alert bracelet, allergy management plan. 2nd generation non-sedating histamine, adrenaline autoinjector, yellow bag, travel letter
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