hypersensitive reactions 2-060806 (report)

7/31/2019 Hypersensitive Reactions 2-060806 (REPORT)

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Type II

Antibody-mediated

cytotoxic hypersensitivity


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The four types of hypersensitive responses

Kuby J et al., Immunology 2003


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Type II hypersensitivity reactions (1)

- Caused by antibody to cell surface antigens

and components of the extracellular matrix.

- These antibodies can sensitize the cells for

antibody-dependent cytotoxic attackby K cells

or for complement-mediated lysis.

- Type II hypersensitivity is seen in the destruction

of red cells in transfusion reactions and inhaemolytic disease of the newborn.


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Type II hypersensitivity reactions (2)

- Innocuous antigens can cause Type II

hypersensitivity reactions insusceptible individuals by binding

to the surfaces of circulating blood cells.

- IgG antibodies against cell-surface receptors

that disrupt the normal functions of the

receptor, either by causing uncontrollable

activation or by blocking receptor function.


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Antibody-Dependent Cell-mediated Cytotoxicity (ADCC)



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ABO blood group



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Development of erythroblastosis fetalis (hemolytic disease of the newborn) caused when an

RH- mother carries an RH+ fetus, and effect of treatment with 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 III

Immune complex-mediated

hypersensitivity


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Type III hypersensitivity reactions (1)

- Directed against soluble antigens

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

- The complexes activate complement and attractploymorphs and macrophages to the site.

- These cells may exocytose their granule contentsand release reactive oxygen and nitrogen

intermediates to cause local tissue damage.


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Type III hypersensitivity reactions (2)

- The deposition of immune complexes in

tissues causes a local inflammatory

response known as an Arthus reaction.

- Serum sickness is a classic example of a

transient immune complex-mediated syndrome.

- In situations in which antigen persists

subacute bacterial endocarditischronic viral hepatitis

systemic lupus erythematosus (SLE)


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Development of a localized Arthus reaction

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


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The multiple activities of the complement system.


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Immune 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 transient

immune complex-mediated syndrome


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Type IV

Delayed-type hypersensitivity (DTH)

(Cell-mediated hypersensitivity)


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Type IV hypersensitivity reactions

- T-cell mediated

- 1st group: Tissue damage is caused by the activationofmacrophages by TH1 cells, which results

in an inflammatory response.

- 2nd group: Damage is caused by the activation by TH2

cells ofinflammatory responses in which

eosinophils predominate.

- 3rd group: Damage is caused directly by cytotoxic T

cells (CTL).


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Figure 12-24

Type IV hypersensitivity responses


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Overview of the DTH response



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Figure 12-26 part 1 of 2

The delayed-type (type IV) hypersensitivity response is directed by

chemokines and cytokines released by TH1 cells stimulated by antigen (1)


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Figure 12-26 part 2 of 2The delayed-type (type IV) hypersensitivity response is directed bychemokines and cytokines released by TH1 cells stimulated by antigen (2)


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A prolonged DTH response can lead to formation of a granuloma

Lytic enzymes released from

activated macrophages in a

granuloma can cause extensivetissue damage.



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A Second Exposure to Poison Oak May Result in Delayed-Type Hypersensitivity


D l t f d l d t h it it ti ft


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

Development of delayed-type hypersensitvity reaction after

a second exposure to poison oak

Secrete INF- and other cytokines

Activated macrophages

Secrete mediatorsof inflammation


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Bli t i ki l i h d f ti t ith


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Figure 12-28

Blistering skin lesions on hand of patient with

poison ivy contact dermatitis


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There are four types of hypersensitivity reaction mediated

by immunological mechanisms that cause tissue damage


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hypersensitive reactions 2-060806 (report)

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