Week 4- Anaphylaxis Flashcards
What is anaphylaxis?
An acute type I hypersensitivity reaction in response to an antigen present throughout the body
What class of antibodies are associated with anaphylaxis?
IgE
What happens during anaphylaxis (in relation to IgE antibodies)
Usually, an antigen encounters a complementary IgM antibody on the surface of a lymphocyte. Antigen binding causes synthesis of IgM and secretion. IgM later develops to IgG, however in a type I hypersensitivity reaction IgE is secreted instead of IgM due to activation of CD4+ T helper cells
IgE binds to mast cells and stimulation of mast cells causes anaphylactic responses
Where are mast cells found?
In connective tissue and in epithelial mucosal tissue but all over the body
What 2 main substances do mast cell granules contain? What types of molecules are these?
Leukotrienes and histamine (inflammatory mediators)
What do inflammatory mediators released by mast cells act on?
Blood vessels and smooth vessels
What effects do mast cell inflammatory mediators have on blood vessels?
They dilate them and increase leakage (oedema)
What effect do mast cell inflammatory mediators have on smooth muscle?
Cause constriction of smooth muscle
How does the anaphylactic response manifest in skin allergy?
Histamine action on blood vessels (dilation etc) causes redness and oedema causes swelling creating rash like appearances
How does the anaphylactic response manifest in hay fever and asthma?
Action of the allergen in the nasal passage connective tissue causes rhinitis ie hay fever. If the allergen reaches the bronchus it causes constriction of the air passage and difficulty in breathing ie asthma
How does the anaphylactic response manifest in food allergies?
Action on the gut connective tissue can cause vomiting and diarrhea and if the agent gets into blood rashes can develop
What type of response is anaphylaxis?
A systemic response to an allergen causing immediate responses around the body
What are the 2 main symptoms in an anaphylactic reaction and how do they arise?
- Shock- the allergen leads to dilation of periphery blood vessels causing a sudden drop in BP resulting in shock
- Difficulty breathing- due to contraction of the smooth muscle in the airway
What are some other symptoms of an anaphylactic reaction?
Nausea, diarrhea, rashes, abdominal cramps
How is anaphylaxis treated?
Patient is laid down with legs elevated to encourage blood supply to the head and trunk.
Adrenaline injection causes constriction of peripheral blood vessels and redirects blood to the organs (epipen)
Antihistamines, anti inflammatory corticosteroids, oxygen and bronchodialators may also be given
