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PM3A > (PM3A) Hypersensitivity > Flashcards

(PM3A) Hypersensitivity Flashcards

1
Q

What is hypersensitivity and autoimmunity?

A

(1) Damage caused by adaptive immune mechanisms

(2) No hazard can be identified

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2
Q

What is the difference between autoimmunity and hypersensitivity?

A

The source of the antigen:
- (1) Internal = autoimmunity
- (2) External = hypersensitivity

Effector mechanism:
- Could be antibody type or T lymphocytes/ cells

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3
Q

What are the types of antibody in effector mechanisms?

A

(1) Binding + blocking

(2) Histamine

(3) Phagocytosis

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4
Q

How are hypersensitivity reactions classified?

A

Classification table

Class 1-4

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5
Q

How does the mediation of class 1-3 compare to that of 4 in hypersensitivity reactions?

A

1-3 = B cell mediated

4 = T cell mediated

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6
Q

Which class of hypersensitivity is most common?

A

Class 1

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7
Q

What is the effector for hypersensitivity class 1 reactions?

A

IgE antibody on mast cells

e.g. hayfever/ asthma/ anaphylaxis

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8
Q

What is the effector mechanism for hypersensitivity class 2?

A

IgM + IgG antibody-mediated cell killing

e.g. mismatched blood transfusion/ haemolytic anaemia of a newborn

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9
Q

What is the effector for hypersensitivity class 3?

A

IgG antibody immune complexes

e.g. serum sickness/ long-term mAb use

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10
Q

What is the effector mechanism for hypersensitivity class 4?

A

T cells (lymphocytes)

e.g. contact dermatitis

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11
Q

What are some triggers of hypersensitivity class 1 responses?

A

(1) Tree pollen

(2) Grass pollen

(3) Flower pollen

(4) Medicines

(5) Latex

(6) Dust mites

(7) Rodents

(8) Birds

(9) Insect bites

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12
Q

Which receptor is present on the outside of mast cells?

A

IgE

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13
Q

What is a sentinel?

A

Another name for a mast cell

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14
Q

What is contained within mast cells?

A

Histamine granules

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15
Q

What triggers histamine release from mast cells?

A

Parasite antigen recognition

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16
Q

What are some common signs and symptoms of a hypersensitivity class 1 response?

A

(1) Swelling

(2) Sneezing

(3) Vasodilation

(4) Itching

(5) Sudden death

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17
Q

Why are mast cells considered antigen specific?

A

Presence of IgE antibodies on surface

Able to recognise parasitic antigens

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18
Q

When are mast cells considered part of adaptive immunity?

A

When they are coated with IgE

To be able to recognise antigens

19
Q

How is hayfever a hypersensitivity reaction?

A

(1) Allergen in upper respiratory tract/ eyes

(2) Itching + sneezing

20
Q

How is asthma a hypersensitivity reaction?

A

(1) Allergen in lower respiratory tract

(2) Causes air vessel constriction

(3) Shortness of breath + wheezing

21
Q

How is anaphylaxis a hypersensitivity reaction?

A

(1) Triggering of sufficient mast cells at the same time

(2) Causes systemic vasodilation

(3) Catastrophic BP drop

(4) Death

22
Q

What is a skin prick test?

A

(1) Drop of liquid purified antigen on skin

(2) Introduce a tiny prick

(3) Small enough to only let a small amount in for a local effect

(4) Must have adrenaline present in case of allergic reaction

23
Q

What is the normal role of IgG and IgM in class 2 hypersensitivity reactions?

A

Killing pathogens

24
Q

What do ‘complement’ proteins do?

A

Punches holes in cell membranes of pathogens

25
Q

How is drug-induced anaemia caused?

A

(1) Drug attaches to red blood cells (erythrocytes)

(2) Antibodies bind to drug

(3) Lyses red blood cells

(4) Causes anaemia

26
Q

What is an example of a high affinity hapten-type reaction?

A

Drug-induced anaemia

27
Q

What are some common drugs that cause drug-induced anaemia?

A

(1) Cephalosporins

(2) Penicillin

(3) Tetracycline

28
Q

What is the normal role of IgG in class 3 hypersensitivity reactions?

A

Neutralising bacterial toxins + viruses

29
Q

What is a class 3 hypersensitivity reaction?

A

Binding of IgG antibodies to bacterial toxins

30
Q

How is antivenom made?

A

(1) Venom taken from snake

(2) Injected into horses

(3) Serum taken from horse is the ‘antivenom’

(4) Can be infused into patient following snakebite
- IF type of snake is known

31
Q

What is likely to occur if large concentrations/ continued use of antivenom occurs?

A

Patient may develop immunity to antivenom (serum sickness)

(Production of antibodies)

Formation of immune complexes

32
Q

What is serum sickness?

A

High levels of antibody

In response to foreign antibody

Systemic inflammatory problems

33
Q

What is a modern alternative to antivenom?

A

Monoclonal antibodies

mAb

34
Q

What type/ class of hypersensitivity is relevant when considering use of monoclonal antibodies?

A

Type/ class 3 hypersensitivity

35
Q

How is hypersensitivity to antivenoms been largely resolved?

A

Monoclonal antibodies

Fully human rather than from horse

36
Q

How are monoclonal antibodies synthesised?

A

(1) Isolation of DNA of a single antibody molecule from millions of B cells

(2) Use of machinery (bioreactor) to upscale production

(3) Injection of pure antibody

37
Q

What are some common examples of antigen target for monoclonal antibodies?

A

(1) Human TNF

(2) Human HER2 receptor

38
Q

What is passive immunisation?

A

Transfer of antibodies into the body

39
Q

What are some disadvantages of antivenom?

A

(1) Horse proteins

(2) Multiple types of antibody

(3) Made in animals

40
Q

What is an example of a class 4 hypersensitivity reaction?

A

Allergic contact dermatitis

41
Q

What is class 4 hypersensitivity? (reaction mechanism)

A

T helper cells

Trigger inflammation

In response to microbial peptides

42
Q

What is delayed-type hypersensitivity?

A

Type/ class 4 hypersensitivity

43
Q

What is the slowest type/ class of hypersensitivity?

A

Type/ class 4

PM3A (36 decks)

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