Chapter 15 Hypersensitivity Reactions. Mast cell. Although the word hypersensitivity implies an increased response, the immune response of a hypersensitivity reaction is not necessarily heightened but instead, an inappropriate response to an antigen. Portier and Richet : - PowerPoint PPT Presentation
Chapter 15 Hypersensitivity ReactionsMast cell
Although the word hypersensitivity implies an increased response, the immune response of a hypersensitivity reaction is not necessarily heightened but instead, an inappropriate response to an antigen.
Portuguese man-of-warPortier and Richet :Anaphylaxis Prophylaxis
Richet was awarded the Nobel Prize in 1913 for the discovery of anaphylaxis.
Four Types of Hypersensitive ResponsesImmediate Hypersensitivity: Type I IgE-mediated hypersensitivity Type II IgG- or IgM-mediated cytotoxic hypersensitivity Type III Immune complex-mediated hypersensitivityDelayed-type Hypersensitivity: Type IV Cell-mediated hypersensitivity
Type I Hypersensitivity - IgE-mediated hypersensitivity
allergen (), allergic ()atopy (), atopic ()
Transfusion Reactions are Type II Reactions
Hemolytic Disease of the New Born is Caused by Type II Reactions
Type IIIHypersensitivitytissue damageLocalized Type III Reaction - Arthus Reaction
Generalized Type III Reaction Serum Sicknessfever, weakness, rashes, edema, erythema, arthritis, glomerulonephritis
Type IV Hypersensitivity Some populations of activated TH cells encounter certain types of antigens, they secrete cytokines that induce a localized inflammatory reaction called delayed-type hypersensitivity (DTH). The term hypersensitivity is misleading, since it suggests that a DTH response is detrimental. Although a DTH response can cause extensive tissue damage in some cases, DTH plays an important role in defense against intracellular pathogens .
Granuloma Formation- Caused by a prolonged DTH response
Contact Dermatitis Is A Type of DTH
formaldehype, trinitrophenol, nickel, turpentine, detergents, poison ivy, poison oak, and active agents in various cosmetics and hair dyes