Hypersensitivity And Allergy Flashcards
What is allergy/ hypersensitivity?
Foreign material recognise but self material damaged
What is autoimmunity?
Self material recognised, self material damaged
What is type 1 allergic tissue damage called?
Reaginic or atopic
What happens if someone produces large amounts of IgE that recognises pollen?
Activates IgE covered mast cells - inflammatory response
What causes smooth muscle contraction (wheezing) in people with pollen allergies
2 IgEs interact with same antigen triggering inflammatory mediators- increase vasodilation and permeability of blood vessels and odema. Resulting in smooth muscle contraction (wheezing)
What is odema?
Movement of plasma and leucocytes int tissue
What are the first mediators of allergic response? How long do they take?
Preformed granules mediators- tryptase, heparin, histamine. 5 min
What are the second mediators of allergic response?
Newly generated mediators- arachidonic acid (5-30 min), leukotrienes and prostaglandins
What is the 3rd response to allergic reaction?
Cytokines- take hours.
How do th2 cells cause an atopic response?
If a th2 cell is sensitive to an antigen it will produce IL-4 that will promote B cells to produce antibodies against it- also produces Il-5 - eosinophils
What type of allergic response are food allergies and allergic rhinitis?
Type 1
In what test will you get a localised wheel and flare?
Skin prick test. If mast cells in tissue are sensitive to allergen- localised wheel and flare
What is type 2 allergic response?
Reaction to cell surface antigens- eg good pastures disease
What is a type 3 allergic response?
Immune complex deposition- eg. SLE
What is type 4 allergic response?
T-cell mediated. Eg. Contact dermatitis
What is atopy?
Family or personal tendency to produce IgE to allergies
What is sensitisation?
IgE response to allergen- blood tes. Can be sensitised but not allergic
Anaphylaxis?
Potentially life threatening allergic reaction- due to cross linking of of IgE bound to mast cell receptors
What is allergy??
Disease following immune response to otherwise innocuous antigen
Anaphylactoid?
Clinically like anaphylaxis but not IgE mediated - release of mast cell contents without cross linking of IgE
What is intolerance?
Non immune related reaction
What two controls are used in a skin prick test?
1) histamine test- make sure patient isn’t taking antihistamines
2) control- nothing- to make sure patient isn’t reacting to prick itself
How do you treat anaphylaxis (at first)?
Oxygen treatment- lay down. Treat with adrenaline if signs of shock
During anaphylaxis if no improvement in 5 min what do you treat with?
Antihistamine
What treatment should a patient t be given to prevent a delayed reaction? (Allergy)
Hydrocortisone - reduces redness and swelling- it is a steroid
How do corticosteroids work to suppress inflammation?
Mimic effect of hormones produced by adrenal glands- suppress immune system. Reduce production of chemicals that cause inflammation
What is an epipen?
A self administered adrenaline device
Should you treat adrenaline though an IV?
No- always IM
What is urticaria?
Chronic or acute (
How do you treat chronic urticaria/angiodema?
Antihistamines for 6mts-1yr. Or T cell inhibitors- cyclosporine
What is cyclosporine?
A t-cell inhibitor.
What do you do if someone has angiodema without urticaria?
Check c3, c4, c1 inhibitor levels
What percentage of the U.K. Suffer from allergic rhinitis?
26%
What can you use to look up a nostril?
An otoscope
How is intermittent and persistent rhinitis divided?
Intermittent. = less than 4 days a week or less than 4 weeks at a time. Mild. = normal sleep and life. Moderate = abnormal sleep and life
What percentage of children and adults have food allergies?
4% children and 3% adults
Give an example of a non immune based food allergy.
Monosodium glutamate- in Chinese foods. Seaweed and tomatoes. Cause headaches, nausea and sweating
What causes oral allergy syndrome?
Local oral symptoms after eating certain foods- veg nuts. Only raw food. Cross reactivity with pollens
What are the two types of vasoactive amines that can cause headaches or palpitations?
Monoamines- chocolate Stilton red wine
Tyramine- yeast extract, soy sauce
What causes coeliac disease?
Due to antibodies to tissue transglutaminase (TTG)
What is involved in desensitisation?
Weekly injections for 15 weeks and 6 weekly injections for 3 years
