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Principles of Immunology Hypersensitivity and Allergy 4/11/06. ”Education is a progressive discovery of our own ignorance”. Will Durant. Word/Terms List. Allergens Atopy Erythroblastosis fetalis Reagin Rhogam Serum sickness Tuberculin skin test. Hypersensitivity and Allergy.

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principles of immunology hypersensitivity and allergy 4 11 06

Principles of ImmunologyHypersensitivity and Allergy4/11/06

”Education is a progressive discovery of our own ignorance”.

Will Durant

word terms list
Word/Terms List
  • Allergens
  • Atopy
  • Erythroblastosis fetalis
  • Reagin
  • Rhogam
  • Serum sickness
  • Tuberculin skin test
hypersensitivity and allergy

Hypersensitivity and Allergy

Hypersensitivity-An exaggerated immune response that may cause damage to the host. The trigger is often an innocuous antigen

Allergy-A hypersensitive response to an environmental antigen. Often presents as “hay fever”, asthma, dermatitis or anaphylaxis.

four types of hypersensitivity
Four types of Hypersensitivity
  • Type I
    • IgE-mediated
    • e.g.most common allergies
  • Type II
    • IgG-mediated
    • e.g.ABO transfusion reaction
four types of hypersensitivity5
Four types of Hypersensitivity
  • Type III
    • Immune-complex mediated
    • e.g.serum sickness
  • Type IV
    • T cell-mediated; delayed type
    • e.g.tuberculin reaction
type i hypersensitivity
Type I Hypersensitivity
  • Allergens
    • Proteins
    • Low molecular weight, soluble
  • Atopy-Predisposition to type I hypersensitivity
    • Higher levels of circulating IgE
    • Greater numbers of eosinophils
type i hypersensitivity8
Type I Hypersensitivity
  • Mechanism
    • Allergen is recognized by naïve B cell
    • B cell stimulated by T helper cell through IL4
    • IgE specific for allergen is recognized by mast cell
    • Cross linkage of IgE on mast cells
    • Mast cell degranulates
mast cell degranulation
Mast Cell Degranulation
  • Leukotrienes
    • Smooth muscle contraction; vascular permeability
  • Platelet activating factor
    • Activates platelets
  • Histamine
    • Vascular permeability; smooth muscle contraction
  • Cytokines
    • IL4- Stimulates T helper response
    • IL3- Activates eosinophils
    • TNF- Promotes inflammation
  • Chemokines
    • MIP- Attracts macrophages
mast cell receptors
Mast Cell Receptors
  • Fc epsilon RI
    • Ig superfamily
    • Alpha, beta and gamma chains
  • Alpha chain
    • Two Ig like domains; extracellular
  • Gamma chain
    • Homodimer; two intracytoplasmic tails
    • ITAMs
  • Cross linkages activates PTKs
    • Cell signaling leads to degranulation
type i hypersensitivity14
Type I Hypersensitivity
  • Clinical manifestations
    • Allergic rhinitis
    • Asthma
    • Food allergies
    • Systemic anaphylaxis
prausnitz kustner reaction
Prausnitz-Kustner Reaction
  • Described in 1921
    • Injected allergen caused specific local reaction (Wheal and flare)
    • Called reagins
    • Later identified in 1960’s to be new class of antibody
    • Rabbit Ab against serum from ragweed sensitive individuals could neutralize allergic reaction
type ii hypersensitivity
Type II Hypersensitivity
  • Cell associated antigens
    • Transfusion reactions
    • Hemagglutinins
    • Complement mediated
    • Clinical symptoms include fever, chills, nausea
type ii hypersensitivity20
Type II Hypersensitivity
  • Erythroblastosis fetalis
    • Rh+ fetus born to Rh- mother
    • First pregnancy sensitizes
    • Subsequent pregnancies result in anti Rh Ab
    • Mild to severe anemia in fetus
    • Rhogam
type ii hypersensitivity22
Type II Hypersensitivity
  • Drug induced hemolytic anemia
    • Some antibiotics can be antigenic
    • Bind nonspecifically to RBC surface proteins
    • Ab fixes C and lyses RBCs
type iii hypersensitivity
Type III Hypersensitivity
  • Soluble antigens complexed with Ab
    • Deposit in tissue or on walls of blood vessels
    • C activation
    • Mast cell binds Fc; degranulates
    • Fc gamma RIII receptors
    • Neutrophils drawn to area; release of lytic enzymes cause type III reaction
type iii hypersensitivity24
Type III Hypersensitivity
  • Serum Sickness
    • Response to foreign protein in serum,e.g horse serum (tetanus antitoxin)
    • Deposition of immune complexes systemically
    • Systemic reactions
    • Fever, vasculitis, arthritis, nephritis
type iii hypersensitivity25
Type III Hypersensitivity
  • Arthus reaction
    • Individual is sensitized to antigen
    • Challenge is administered locally
    • Reaction occurs locally
    • Mast cell mediated
type iv hypersensitivity
Type IV Hypersensitivity
  • T cell mediated
    • T helper 1 cells
    • Effector response is through macrophages not T cytotoxic cells
    • Cytokine mediated
      • IL3 Hematopoiesis
      • Interferon, TNF, IL 1 Extravasation
      • MCAF Attracts macrophages
      • MIF Retains macrophages