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17 Cards in this Set

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What are the 4 subdivision of hypersensitivity disorders?
• Type I: Immediate hypersensitivity disorder
• Type II: antibody-mediated disorders
• Type III: immune complex-mediated disorders
• Type IV: T-cell-mediated disorders
What is the mechanism of type I hypersensitivity disorders?
IgE-mediated hypersensitivity that leads to the release of inflammatory mediators for sensitized mast cells
Name and describe the 2 phases of type I hypersensitivity reactions
1. Primary early response: characterized by vasodilation, vascular leakage, and smooth muscle contraction

2. Secondary or late phase response: chaharcterized by more intense infiltration of tissues w/ eosinophils & epithelial cell damage
What is an anaphylactic reaction?
• a systemic life-threatening hypersensitivity reaction
• characterized by edema in many tissues and a fall in BP secondary to vasodilation
What is an atopic reaction?
• a type I reaction when the antigen is confined to a particular site
• refers to a genetically determined hypersensitivity to common environmental allergens
What are some common atopic disorders?
• urticaria (hives)
• allergic rhinitis (hay fever)
• atopic dermatitis
• food allergies
• some forms of asthma
What are characteristics of type II hypersensitivity reactions?
• mediated by IgG or IgM antibodies directed againsts antigens on the surface of cells
• examples include mismatched blood transfusion rxns, ABO or Rh incompatibility, and certain drug reactions
What are characteristics of type III hypersensitivity reactions?
• mediated by the formation of insoluble antigen-antibody complexes that activate complement
• generates chemotactic and vasoactive mediates that cause tissue damage by alering blood flow, increasing vascular permability, and inducing an inflammatory response
What are examples of type III hypersensitivity reactions?
• Post-streptococcal glomerulonephritis
• Osler nodes of endocarditis
What type of hypersensitivity reaction involve T-cell mediated immune responses?
Type IV
What are the 2 basic types of type IV hypersensitivity reactions?
• direct cell-mediated cytotoxicity
• delayed-type hypersensitivity disorders
Describe direct cell-mediated cytotoxicity
• CD8+ cytolytic T lymphocytes (CTLs) directly kill the antigen-presenting target cells
Describe delayed-type hypersensitivity reactions
cytokines promote differentiation & activation of macrophages that function as phagocytic and antigen-presenting cells
What are examples of a type IV delayed-type hypersensitivity reaction?
• Purified protein derivative (PPD)
• Allergic contact dermatitis
• Hypersensitivity Pneumonitis
What is the most common type of allergic reaction to latex?
a contact dermatitis caused by a type IV delay-type hypersensitivity
What is self-tolerance?
the ability of the immune system to differentiate self from non-self
what causes B-cells to produce IgE?
stimulation by an antigen-stimulated T-H2 cell