Anaphylactic Reaction Flashcards
What type of reaction is anaphylaxis?
Acute type I hypersensitivity reaction.
What does anaphylaxis result from?
Ig-E mediated response to an allergen found throughout the body. It is a systemic response to allergen.
What is the difference in lymphocyte activation in anaphylaxis to normal?
Normally antigen binds to surface IgM on lymphocytes stimulating secretion of antibody. Initially secretes IgM and this then switches to IgG.
In type I hypersensitivity, IgM switches to IGE when CD4+ T helper cells are stimulated.
What cells does IgE bind to?
Binds to Ig-E receptors on the surface of mast cells, stimulating degranulation.
What inflammatory mediators do mast cells contain?
Histamine and leukotrienes.
What effect does histamine have in connective tissue?
Causes dilation of vessels with increased blood flow to the surface and increased movement of fluid out of the blood.
What effect does histamine have around mucosae?
Constriction of airways and contraction of smooth muscle in the walls of the intestines.
What occurs in skin allergy?
Stimulation of mast cells in connective tissue causes vasodilation leading to redness and odema leading to its raised appearance. Rash called urticaria.
How are hay fever symptoms caused?
If allergen is inhaled. site of action is mucosal mast cells of respiratory system.
Odema in epithelia lining the nose.
Irritation inducing stimulation of mucus secretion.
How are asthma symptoms caused?
Allergen reaches bronchioles of the lungs.
Contraction of smooth muscle reducing diameter of airways.
Inflammation and increased mucus production.
Food allergies
Allergen ingested.
Act at mucosal mast cells in intestinal tract.
Stimulates smooth muscle leading to vomiting and diarrhoea.
If absorbed into blood stream, causes skin symptoms.
Changes in body associated with anaphylaxis
Dilation of peripheral blood vessels causes symptoms of rashes, odema and DECREASED BLOOD PRESSURE = SHOCK
Constriction of bronchi causing difficulty breathing.
What is the emergency treatment for anaphylaxis?
First try to aleviate low blood pressure:
Patient lain down with feet raised to increase blood flow to head and trunk.
Adrenaline injection to constrict peripheral blood vessels - blood flow to organs instead.
Intravenous drip.
Treat inflammation:
Antihistamines
Anti-inflammatory corticosteroids
Oxygen and bronchodilators.
