Johanna @jmhofmann
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immunology pathophysiology anaphylaxis allergy hypersensitivityreaction management treatments type4 typeiv
Anaphylaxis: Pathogenesis Anaphylaxis is a Type 1 hypersensitivity reaction While the primary mechanism of anaphylaxis is mast cell
Anaphylaxis: Pathogenesis Anaphylaxis is a Type 1 hypersensitivity reaction While the primary mechanism of anaphylaxis is mast cell activation, basophils and eosinophils may also play a role Inappropriate mast cell activation => Immediate Phase (seconds-minutes) => Mast cell degranulation -> release of preformed mediators => • Histamine • Lipid mediators (e.g. prostaglandins, leukotrienes) • Other mediators (e.g. PAF, tryptase, TNF) • Additional production of inflammatory mediators (e.g. cytokines, chemokines) => • Vasodilation • Increased vascular permeability • Smooth muscle contraction in airways • Increased mucus secretion • Recruitment of inflammatory cells • ANS activation => Anaphylaxis #Anaphylaxis #pathophysiology #immunology
Anaphylaxis: Treatments (Acute) Additional Info: • IV steroids may be considered for prevention of late phase reactions.
Anaphylaxis: Treatments (Acute) Additional Info: • IV steroids may be considered for prevention of late phase reactions. Patients should be monitored in the ED for a minimum of 4-6 hrs. • Follow-up with a family physician is suggested within 48hrs. An epinephrine autoinjector prescription should be provided, as well as allergy testing. • H2 receptor antagonist use (e.g. Ranitidine), to amplify H1 receptor antagonist responses may be considered. Beta-blockers and IV fluids for blood pressure resuscitation may also be warranted. Treatment: • Antihistamine (adjunct therapy) e.g. Cetirizine (non-sedating) PO q4-6hrs • Epinephrine (1st line treatment) 1:1000 IM q5-10mins, anterolateral thigh • Salbutamol (adjunct therapy) e.g. Ventolin inhaler #Anaphylaxis #Treatments #Management #pathophysiology #immunology
Type IV Hypersensitivity: Pathogenesis and clinical findings Definition: Unique because it is entirely T-Cell mediated; exposure to
Type IV Hypersensitivity: Pathogenesis and clinical findings Definition: Unique because it is entirely T-Cell mediated; exposure to allergen causes development of allergen-specific T-Cell response. Allergic reaction develops several days after exposure, because T-Cell activation takes time. Initial exposure to allergen (typically a drug) -> Macrophage engulfs antigen -> Antigen presentation on MHC II molecule -> Particular CD4+ Th cells recognize antigen on allergen's surface as potentially harmful -> Th Cells activate macrophages, mast cells or CTLs -> Inflammation and destruction of involved issue => • Stevens-Johnson Syndrome • Contact Dermatitis (Ex. Poison ivy) #TypeIV #Type4 #HypersensitivityReaction #Allergy #Immunology #pathophysiology
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