Chapter 15 Hypersensitivity Reactions

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Chapter 15 Hypersensitivity Reactions
Mast cell
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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.
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Portier and Richet Anaphylaxis ????
? Prophylaxis ?? Richet was awarded the Nobel
Prize in 1913 for the discovery of anaphylaxis.
Portuguese man-of-war
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Four Types of Hypersensitive Responses Immediate
Hypersensitivity Type I IgE-mediated
hypersensitivity Type II IgG- or
IgM-mediated cytotoxic
hypersensitivity Type III Immune
complex-mediated hypersensitivity Delayed-type
Hypersensitivity Type IV Cell-mediated
hypersensitivity
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Type I Hypersensitivity - IgE-mediated
hypersensitivity
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allergen (???), allergic (???) atopy (????),
atopic (???????)
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Transfusion Reactions are Type II Reactions
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Hemolytic Disease of the New Born is Caused by
Type II Reactions
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Type III Hypersensitivity
Localized Type III Reaction - Arthus
Reaction
tissue damage
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Generalized Type III Reaction Serum Sickness
fever, weakness, rashes, edema, erythema,
arthritis, glomerulonephritis
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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 .
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Granuloma Formation - Caused by a prolonged DTH
response
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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
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Summary