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Immunology & Serology > Hypersensitivity > Flashcards

Hypersensitivity Flashcards

1
Q

Hypersensitivity Reactions

A

an exaggerated response to a harmless antigen

reaction dependent on host’s response

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2
Q

Sensitization

A

hypersensitivity reactions that occur in subjects previously exposed to Ag who have developed immune response

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3
Q

Allergy

A

2 forms of hypersensitivity can occur in response to different types of Ag
Type 1 - immediate type
type 4- delayed type

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4
Q

Type 1 hypersensitivity reaction

A

immediate hypersensitivity reaction (2-30 minutes)

mediated by IgE antibodies!!

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5
Q

Step 1 of Type 1 hypersensitivity

A

allergen is presented to CD4+ (Th2 subtype)

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6
Q

Step 2 of Type 1 hypersensitivity

A

stimulates B cell production of IgE Abs

produces a large amount of IgE in response to a small concentration of antigen

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7
Q

Step 3 of Type 1 hypersensitivity

A

Sensitization phase!
IgE Abs attach at the Fc end to mast cells of the tissues & basophils in the blood
IgE remains dormant attached to these cells
IgE serves as an antigen receptor

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8
Q

Step 4 of Type 1 hypersensitivity

A

when exposed to allergen a second time

antigens combine with IgE Abs on the surface of mast cells & basophils & release histamines & serotonins

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9
Q

Clinical Manifestations of Type 1 hypersensitivity

A

can be localized & systemic

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10
Q

Allergic Asthma

A

type 1 :

coughing, wheezing, shortness of breath etc

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11
Q

Atopic Dermatitis

A

type 1:
itchy, red skin rash,
chronic lesions w/ thickened skin may develop

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12
Q

Urticaria

A

Type 1:
commonly associated with allergies to latex, foods, drugs
widespread, itchy, white areas surrounded by redness ‘wheal & flare’

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13
Q

Gastrointestinal Reactions

A

Type 1:

usually associated with food allergies, nausea, vomiting, abdominal pain, etc

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14
Q

Systemic Anaphylaxis

A

Type 1:
potentially life-threatening
seconds or minutes, can involve multiple organ systems

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15
Q

Type 1 testing

A
  1. in vivo methods - direct skin testing

2. in vitro methods - lab testing serum of total IgE

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16
Q

In Vitro Allergy test

A

for type 1 hypersensitivity:

  1. radioimmunosorbent test RIST- total IgE
  2. radioallergosorbent test RAST - allergen specific IgE
17
Q

Type 1 treatment

A

avoid allergen
block allergen response
immunotherapy - desensitization or allergy shots

18
Q

Type 2 hypersensitivity

A

reaction caused by the reaction of IgG and IgM with cells and tissues
antibody dependent & complement mediated

19
Q

Type 2 Clinical Manifestations

A
  1. transfusion reactions
  2. hemolytic disease of the newborn
  3. hemolytic anemias - autoimmune
20
Q

Hemolytic transfusion reaction

A

type 2 hypersensitivity

massive complement activation, hemolysis, shock, death etc etc

21
Q

Type 2 testing

A

Direct Antiglobulin test (DAT)

agglutination is positive

22
Q

Type 3 hypersensitivity

A

immune complex formation

IgG or IgM antibodies - complement mediated

23
Q

Step 1 of type 3 hypersensitivity

A

soluble antigen combines with soluble antibody, immune complexes are formed & precipiate out of the serum

24
Q

Step 2 of type 3 hypersensitivity

A

in the tissues the immune complexes bind complement

25
Q

step 3 of type 3 hypersensitivity

A

complement activation results in histamine/cytokine activation

26
Q

step 4 of type 3 hypersensitivity

A

neutrophils migrate to site & release granules causing chronic inflammation & tissue destruction

27
Q

Type 3 clinical manifestations

A

lupus,
post streptoccoal glomerulnephritis,
reactive arthritis
farmer’s lung

28
Q

Type 3 testing

A

look for immune complex (Ig) deposition in tissues with immunohistochemistry

29
Q

Type 4 hypsersensitivity

A

delayed hypersensitivity (2-3 days)
no antibody involved
mediated by CD4+ Th1 T cells & CD8+ cells

30
Q

Sensitization phase of type 4 hypersensitivity

A
  1. antigen contact
  2. 1-2 weeks after initial contact: antigen processed & presented to antigen specific Th cells & they then activate & proliferate
    these cells are called delayed-type hypersensitivity T cells
31
Q

Effector phase of type 4 hypersensitivity

A

next antigen exposure, production of variety of cytokines & chemokines
attract monocytes & PMNs
inflammatory response follows, results in tissue damage, granulomas, & necrosis

32
Q

Contact Dermatitis

A

Type 4:

skin reaction caused by contact w/ a variety of agents

33
Q

Hypersensitivity Pneumonitis

A

Type 4:

inhalation of allergen, most cases occupational - farmer’s lung etc

34
Q

M. TB screening test (Mantoux test)

A

Type 4 reaction

positive result suggests an individual has been exposed

Immunology & Serology (9 decks)

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