This document discusses anaphylaxis, which is an acute allergic reaction caused by re-exposure to an antigen that elicits an IgE-mediated response. It often results from exposure to medications, foods, or insect stings. The reaction occurs when IgE antibodies bind to mast cells and basophils, and cross-linking by the antigen leads to degranulation and release of inflammatory mediators such as histamine. Common symptoms include bronchospasm, edema, cardiac issues, and gastrointestinal problems. Treatment focuses on relieving symptoms through epinephrine, antihistamines, fluids, and desensitization to prevent future reactions.

1. AnAphylAxisAnAphylAxis
IgE Mediated
Hypersensitivi
ty

2. WhAtWhAt is AnAphylAxis?is AnAphylAxis?
 An acute systemic allergic reactionAn acute systemic allergic reaction
 The result of a re-exposure to an antigenThe result of a re-exposure to an antigen
that elicits an IgE mediated responsethat elicits an IgE mediated response
 Usually caused by a common environmentalUsually caused by a common environmental
protein that is not intrinsically harmfulprotein that is not intrinsically harmful
 Often caused by medications, foods, andOften caused by medications, foods, and
insect stingsinsect stings
 It is a Type I hypersensitivityIt is a Type I hypersensitivity

3. historyhistory
 1st recorded 2640BC in hieroglyphics1st recorded 2640BC in hieroglyphics
– bee sting of a pharoahbee sting of a pharoah
 Richet & PortierRichet & Portier
– South SeasSouth Seas
– Man-o-warMan-o-war
– coined term anaphylaxiscoined term anaphylaxis

4. igEigE
 Binds irreversible to FcBinds irreversible to FcεεRI receptors onRI receptors on
mast cells, basophils, and eosinophilsmast cells, basophils, and eosinophils
 Is usually for parasitic infectionsIs usually for parasitic infections
 E heavy chainE heavy chain

7. MAst CEllMAst CEll
 Has high affinity for IgE molecules (105 IgE/cell)Has high affinity for IgE molecules (105 IgE/cell)
 Originates in the bone marrow, reside inOriginates in the bone marrow, reside in
connective tissuesconnective tissues
 Increases host response to parasitic infectionsIncreases host response to parasitic infections
 Contain immunological mediators in granules ie.Contain immunological mediators in granules ie.
Histamine, ECF-A, HMW-NCFHistamine, ECF-A, HMW-NCF
 2 populations that vary in granule content and2 populations that vary in granule content and
activityactivity
– Connective tissueConnective tissue
– MucosalMucosal

10. IgE FcRI REcEptoRIgE FcRI REcEptoR

11. SymptomSSymptomS
 Peripheral vasodilationPeripheral vasodilation
– vascular permeablility (edema)vascular permeablility (edema)
 BronchospasmBronchospasm
 Cardiac arrhythmiasCardiac arrhythmias
 Smooth muscle contractionsSmooth muscle contractions

12. SEnSItIzatIonSEnSItIzatIon
 Antigen is presented by antigen presentingAntigen is presented by antigen presenting
cellscells
 TTHH2 cells induce B cell activation2 cells induce B cell activation
– CD40 ligand and cytokinesCD40 ligand and cytokines
 B cells undergo isotype switching andB cells undergo isotype switching and
produce antibodyproduce antibody
 Serum antibody is bound by the mast cellsSerum antibody is bound by the mast cells

13. thE allERgIc RESponSEthE allERgIc RESponSE
 Secondary presentation of antigen producesSecondary presentation of antigen produces
anan immediateimmediate response controlled by mastresponse controlled by mast
cellscells
 Granule contents are releasedGranule contents are released
 Cell mediated response proceedsCell mediated response proceeds

14. SEnSItIzatIon & RESponSESEnSItIzatIon & RESponSE

15. What is happening?What is happening?
 Initial exposure sensitizes mast cells.Initial exposure sensitizes mast cells.
 Antigen specific IgE molecules attach toAntigen specific IgE molecules attach to
high affinity Fc receptors on the mast cellhigh affinity Fc receptors on the mast cell
surface.surface.
 Cross linking of IgE molecules on surfaceCross linking of IgE molecules on surface
causes intracellular signaling pathwaycauses intracellular signaling pathway
– Inflammatory mediators are released uponInflammatory mediators are released upon
degranulationdegranulation

17. Mediators involvedMediators involved
 Include histamine, proteases, chemotacticInclude histamine, proteases, chemotactic
factors, leukotrienes, prostaglandin D, andfactors, leukotrienes, prostaglandin D, and
cytokinescytokines
 Primary: released before degranulationPrimary: released before degranulation
– Interleukin 4 used by T cells induces B cellInterleukin 4 used by T cells induces B cell
maturationmaturation
– IL-3 and IL-5 released by T and mast cells areIL-3 and IL-5 released by T and mast cells are
chemo attractants for eosinophilschemo attractants for eosinophils
 Secondary: come from granulesSecondary: come from granules

20. histaMinehistaMine
 Synthesized and stored in granulesSynthesized and stored in granules
 The primary mediator in the granulesThe primary mediator in the granules
 3 receptors3 receptors
– H1: Smooth muscle & endotheliumH1: Smooth muscle & endothelium
 Increased IP3 & DAGIncreased IP3 & DAG
– H2: Gastric mucosa, cardiac muscle, mast cellsH2: Gastric mucosa, cardiac muscle, mast cells
 Increased cAMPIncreased cAMP
– H3: Pre-synaptic brainH3: Pre-synaptic brain
 Decreases histamine releaseDecreases histamine release

21. tissue effects of histaMinetissue effects of histaMine
 CardiovascularCardiovascular
– Decreased blood pressureDecreased blood pressure
– Increased heart rateIncreased heart rate
– Edema (separation of endothelial cells &Edema (separation of endothelial cells &
increased permeability)increased permeability)
 RespiratoryRespiratory
– broncho constrictionbroncho constriction
 GastrointestinalGastrointestinal
– Smooth muscle contraction and diarrheaSmooth muscle contraction and diarrhea
 SkinSkin
– UrticariaUrticaria

22. TreaTmenTsTreaTmenTs
 AntihistaminesAntihistamines
– Block H1 and H2 receptorsBlock H1 and H2 receptors
 Epinephrine for bronchospasmsEpinephrine for bronchospasms
– stimulates the reformation of tight junctionsstimulates the reformation of tight junctions
between endothelial cellsbetween endothelial cells
 IV fluids to support blood pressureIV fluids to support blood pressure
 DesensitizationDesensitization

23. anT biTesanT biTes
 Red Imported Fire AntRed Imported Fire Ant
 Venom (antigen)Venom (antigen)
– Composed largely of low MW alkaloids, alsoComposed largely of low MW alkaloids, also
different proteinsdifferent proteins
– Each component is able to induce anaphylaxisEach component is able to induce anaphylaxis
 Able to inject 100ng venom/biteAble to inject 100ng venom/bite
 Venom induces venom specific IgE antibodyVenom induces venom specific IgE antibody
productionproduction

25. Done by :Done by :
Ghadah SidqiGhadah Sidqi
G(G(33)) ,, L(L(55)) ..