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Integrative > 9) Hypersensitivity Reactions > Flashcards

9) Hypersensitivity Reactions Flashcards

1
Q

What is a hypersensitivity reaction?

A

Antigen-specific immune responses that are either inappropriate or excessive and result in harm to the host

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2
Q

Give examples of triggers for hypersensitivity reactions:

A

Exogenous: non infectious substances, infectious microbes, drugs
Intrinsic: infectious microbes, self antigens

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3
Q

What are type I hypersensitivity reactions (basic)?

A

Immediate (allergy) - environmental non infectious antigens

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4
Q

What are type II hypersensitivity reactions (basic)?

A

Antibody mediated reactions

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5
Q

What are type III hypersensitivity reactions (basic)?

A

Immune complex mediated reactions

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6
Q

What are type IV hypersensitivity reactions (basic)?

A

Cell mediated (delayed) reactions

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7
Q

What is the sensitisation phase of a hypersensitivity reaction?

A

First encounter with antigen

Activation of APCs and memory effector cells

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8
Q

What is the effector phase of a hypersensitivity reaction?

A

Pathologic reaction upon re-exposure to same antigen

Activation of memory cells of adaptive immunity

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9
Q

What are the mechanism behind type II hypersensitivity reaction?

A 
Antibody mediated (IgM or IgG)
Develops with 5-12 hours 
Target cell bound antigens causing tissue/cell damage or physiological change
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10
Q

What are some examples of type II hypersensitivity reactions?

A 
Haemolytic disease of the newborn 
Transfusion reactions 
Goodpasture's
Graves'
Myasthenia gravis
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11
Q

Describe haemolytic transfusion reaction:

A

Incompatibility in ABO group or rhesus D antigens causing RBC lysis by type II hypersensitivity reaction involving IgM
Shock, kidney failure, circulatory collapse

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12
Q

Describe the mechanism behind haemolytic disease of the newborn:

A

Rhesus negative mother with rhesus positive fetus
Rhesus antigens from fetus enter mother’s blood during delivery so mother produces anti-rhesus antibodies
If woman becomes pregnant with another rhesus positive fetus, her antibodies will cross placenta and damage fetal RBCs

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13
Q

Explain the direct Coombs test:

A

Used to detect antibodies bound to surface or RBCs
Blood sample taken and washed to remove patient’s plasma, then incubated with anti-human globulin. If RBCs agglutinate, positive test

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14
Q

Explain the indirect Coombs test:

A

Detects antibodies against RBCs in patient’s serum
Serum extracted from blood sample of patient and incubated with RBCs of known antigenicity. Anti-human globulin added and if agglutination occurs, test is positive

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15
Q

What are some therapeutic approaches to type II hypersensitivity reactions?

A 
Immunosuppression
Plasmaphresis
Splenectomy 
IV immunoglobulin 
Replacement therapy
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16
Q

Explain plasmaphresis therapy:

A

Blood removed from the patient, plasma removed from blood and is treated before being returned to patient

17
Q

What factors affect immune complex pathogenesis in type III hypersensitivity reactions?

A

Complex size
Host response
Local tissue factors

18
Q

What are some examples of diseases caused by type III hypersensitivity reactions?

A

Rheumatoid arthritis (IgM)
Glomeurlonephritis
SLE

19
Q

What are the subtypes of type IV hypersensitivity reactions?

A

Contact hypersensitivity
Tuberculin hypersensitivity
Granulomatous hypersensitivity

20
Q

What are some diseases caused by type IV granulomatous hypersensitivity reactions?

A

TB
Leprosy
Schistosomiasis
Sarcoidosis

21
Q

What are some diseases caused by type IV contact hypersensitivity reactions?

A

Nickel
Poison ivy
Organic chemicals

22
Q

What are some diseases caused by type IV autoimmune hypersensitivity reactions?

A

Diabetes
Hashimoto’s
Rheumatoid arthritis (IgG)

23
Q

What are some therapies for type III and IV hypersensitivity reactions?

A 
Corticosteroids
Azathioprine
Mycophenolate mofetil
Cyclophosphamide 
Monoclonal antibodies

Integrative (9 decks)

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