While hunting, a 45-year-old Caucasian male is stung by a bee. He begins to feel unwell and is taken to the hospital. Upon arrival, it is noted that the patient is hypotensive with a blood pressure of 60/40 mmHg. Furthermore, the patient is tachycardic and edematous. What is responsible for this patient’s presentation?
1.Free IgE binding to the antigen
2.IgE on must cell surfaces binding to the antigen
3.IgE activation of complement
4.complexes of IgE binding to the antigen
5.IgE on eosinophils binding to the antigen
sol:
The patient is experiencing systemic anaphylaxis from the bee sting. The direct effect in a sensitized individual antigen challenge is cross-linking of IgE antibodies on the surface of mast cells, resulting in the systemic activation and degranulation of mast cells.
Anaphylactic and atopic reactions are two variants of Type I hypersensitivity reactions. In Type I response, previous exposure to an antigen results in the B-cell production of IgE antibodies, that then bind to Fc receptors on the surface of mast cells. Upon repeat exposure to the antigen, the antigen binds to IgE coated on the surface of mast cells and cross links the antibodies; the result is activation of the mast cell and subsequent degranulation of inflammatory mediators.
Simons investigates the current treatment of anaphylaxis. He notes that the incidence of anaphylaxis is increasing. Foods, medications, and insect stings are the most common triggers. Long-term risk reduction in patients susceptible to anaphylaxis includes optimal mangement of relevant comorbidities such as respiratory and cardiovascular disease, as well as relevant immunomodulation through the use of desensitization, and venom immunotherapy.
Tang describes a practical guide to anaphylaxis. It is a reaction with respiratory, cardiovascular, cutaneous, and gastrointestinal infections that results in 1500 deaths per year in the US. Prompt treatment is important, beginning with intramuscular epinephrine (Epi-pens) and intravenous fluid. Additionally, monitoring of the airway and antihistamine/steroid pharmacotherapy are necessary.
Illustration A diagrams the role of the mast cell in response to allergy.