hypersens 2 Flashcards
What type of cell causes these symptoms?
He was nauseous and felt dizzy, and his skin felt hot and started itching. By the time his girlfriend came home from work he was puffy round the eyes with obvious rashes on his skin
Mast cell
What is the signalling molecule involved?
Histamine
Mast cells are widely distributed throughout the body
connective tissue (e.g. under the skin) and in association with epithelial mucosae (e.g. the respiratory and intestinal epithelia)
what prominent inflammatiry mediaters do they contain
They contain prominent granules which contain a number of mediators of inflammation, notably histamine and leukotrienes
where do the im act and cause
act principally on blood vessels and smooth muscle. In connective tissue histamine causes dilatation of vessels with increased blood flow to the surface and increased movement of fluid out of the blood stream (oedema). Around mucosae the opposite effect occurs, causing constriction of airways and contraction of the smooth muscle in the walls of the intestines.What immunoglobulin class is likely to be involved?
What immunoglobulin class is likely to be involved?
Immunoglobulin E
Histamine and leukotrienes are secreted following antigen binding to the cell surface IgE.
The IgE response is thought to be important in defence against certain
parasitic infections (e.g. nematodes)
What causes the rashes and puffy skin?
the patient has a skin allergy, stimulation of connective tissue mast cells causes vasodilatation leading to the red colour of the skin rash, and oedema leading to its raised appearance.
what is the rash called
This type of rash is often called urticaria and is familiar as the pattern of rash caused by stinging nettles.
what reaction in seen in a allergy skin test
The localised skin reaction is used in allergy testing, where small amounts of possible allergens are injected by pin-prick to see if they cause this kind of localised wheal-and-flare reaction
what happens in Hay fever
If the allergen is inhaled, the principal site of action will be mucosal mast cells of the respiratory system. If this is principally in the nasal passages, the effect will be oedema in the epithelia lining the nose and a consequent general irritation including stimulation of mucus secretion. It is the allergic reaction which causes hay fever (allergic rhinitis)
asthmaa
If the allergen reaches the bronchioles of the lungs then there will be contraction of smooth muscle reducing the diameter of the airways, as well as inflammation and increased mucus production. The result is asthma, with difficulty breathing in and (especially) breathing out.
Food allergies
If the allergen is ingested, then it will act at mucosal mast cells in the intestinal tract. The stimulation of the associated smooth muscle leads to the vomiting and diarrhoea typical of a food allergy. If the allergic substance can be absorbed and pass into the blood stream it may also cause skin symptoms (rashes or itching).
Why should adrenaline have been given?
an injection of adrenaline will act to constrict peripheral blood vessels and redirect blood to the organs.
What sorts of drugs might have been in the subsequent injections?
Medications that may be used subsequently include antihistamines e.g. diphenhydramine and anti-inflammatory corticosteroids e.g. hydrocortisone.
If breathing problems persist, oxygen may be necessary and bronchodilators may be given via an inhaler e.g. salbutamol.
