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Type I I

Antibody-mediated

cytotoxic hypersensitivi ty

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The four types of hypersensi tive responses

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Type I I hypersensi tivity reactions (2)

- Innocuous antigens can cause Type II

hypersensitivity reactions insusceptible individuals by bindingto the surfaces of circulating blood cells .

- IgG antibodies against cell-surface receptorsthat disrupt the normal functions of thereceptor, either by causing uncontrollableactivation or by blocking receptor function .

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Antibody-Dependent Cell-mediated Cytotoxici ty (ADCC)

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ABO blood group

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Development of erythroblastosis fetalis (hemolytic disease of the newborn) caused when anRH - mother carr ies an RH + f etus, and effect of treatment wi th anti -Rh antibody, or Rhogam

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Graves’ disease: Hyperthyroidism Myasthenia gravis: Muscle weakness

(hormones) (neurotransmitter)

Effector mechanisms of antibody-mediated disease

C

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Type I I I

I mmune complex-mediated

hypersensitivity

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The four types of hypersensi tive responses

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Type I I I hypersensi tivi ty reactions (1)

- Directed against soluble antigens

- Caused by the deposition of antigen/antibodycomplexes in tissue and blood vessels .

- The complexes activate complement and attract ploymorphs and macrophages to the site.

- These cells may exocytose their granule contentsand release reactive oxygen and nitrogenintermediates to cause local tissue damage .

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Type I I I hypersensi tivi ty reactions (2)

- The deposition of immune complexes intissues causes a local inflammatoryresponse known as an Arthus reaction .

- Serum sickness is a classic example of atransient immune complex-mediated syndrome.

- In situations in which antigen persistssubacute bacterial endocarditischronic viral hepatitissystemic lupus erythematosus (SLE)

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Development of a local ized Ar thus reaction

Immunology (Fig. 16-15), 5th edn 2003 Kuby J

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I mmune complex disease

- The immune complexes produced may bind to vascular endothelium and kidney glomeruli and activate complement(MAC generation).

- It initiates the acute inflammatory responses that destroy the

vessel walls or glomeruli and lead to thrombosis, ischemicdamage to tissues, and scarring.

- Some of the late complement proteins may activate prothrombinases in the circulation that initiate thrombosis .

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Figure 12-23

Serum sickness is a classic example of a tr ansient

immune complex-mediated syndr ome

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Type I V

Delayed-type hypersensitivi ty (DTH )

(Cell-mediated hypersensitivi ty)

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The four types of hypersensi tive responses

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Type I V hypersensi tivity reactions

- T-cell mediated

- 1st group: Tissue damage is caused by the activationof macrophages by TH1 cells , which resultsin an inflammatory response .

- 2nd group: Damage is caused by the activation by TH2cells of inflammatory responses in whicheosinophils predominate.

- 3rd group: Damage is caused directly by cytotoxic Tcells (CTL) .

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Figure 12-24Type I V hypersensi tivity r esponses

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Overview of the DTH response

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Figure 12-26 part 2 of 2The delayed-type (type I V) hypersensitivity r esponse is directed bychemoki nes and cytoki nes released by TH 1 cells stimulated by anti gen (2)

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A prolonged DTH response can l ead to formation of a granuloma

L ytic enzymes released f rom activated macrophages in a

granuloma can cause extensive ti ssue damage.

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A Second Exposure to Poison Oak M ay Result in Delayed-Type H ypersensi tivity

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D l fd l d h i i i f

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Immunology (Fig. 16-20), 5th edn 2003 Kuby J

Development of delayed-type hypersensi tvity reaction aftera second exposure to poi son oak

Secrete INF- γ and other cytokines

Activated macrophages

Secrete mediatorsof inflammation

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Figure 12-28

Blister ing ski n lesions on hand of patient withpoison ivy contact dermati ti s

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There are four types of hypersensi tivity r eaction mediatedby immunological mechanisms that cause ti ssue damage

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Kuby J et al., Immunology 2003

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