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Inflammation and Immunity > 2.1.2 Hypersensitivity > Flashcards

2.1.2 Hypersensitivity Flashcards

1
Q

What is a hypersensitivity?

A

Excessive or aberrant pathologic immune reactions

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2
Q

What is the Gel and Coombs classification for Type I hypersensitivities?

A

Immediate hypersensitivity Mast cell-derived mediators

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3
Q

What is the Gel and Coombs classification for Type II hypersensitivities?

A

Antibody-mediated cytotoxicity IgM or IgG antibodies against cell surface or extracellular matrix antigens

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4
Q

What is the Gel and Coombs classification for Type III hypersensitivities?

A

Immune complex-mediated diseases Deposition of immune complexes in vascular basement membrane. Soluble Ags

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5
Q

What is the Gel and Coombs classification for Type IV hypersensitivities?

A

T cell-mediated T cells and autoimmunity

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6
Q

Type I hypersensitivity is mediated by what?

A

IgE-mast cell

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7
Q

Type I hypersensitivities are characterized by what?

A

Allergy or atopy; Rapid vascular leakage (inflammation); Hay fever, food allergies, asthma, or anaphylaxis

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8
Q

Upon activation Mast cells degranulate, what are they releasing?

A

Histamine

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9
Q

What are some of the lipid mediators that mast cells release?

A

Prostaglandin and leukotrienes

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10
Q

What is an important cytokine that mast cells release when activated?

A

TNF-alpha

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11
Q

What is the pathway that happens in a type I hypersensitivity upon exposure to pollen?

A

First exposure to the allergen will cause binding to the B cell. This will lead to signaling to the Th2 cells and stimulate IgE class switching in B cells. IgE will be produced, and will bind to the Fc-epsilon-RI on mast cells. Upon second exposure to this allergen, the allergen will bind to multiple receptors on the mast cell signaling for the release of mediators.

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12
Q

Upon FceRI crosslinking by antigen on a mast cell what signaling occurs?

A

Phosphorylation of Lyn kinase then subsequent phosphorylation of Syk kinase

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13
Q

Phosphorylated Syk will carry out what function?

A

Phosphorylation of PLC-gamma

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14
Q

PLC-gamma activation will then do what in mast cells?

A

Create IP3 and DAG

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15
Q

What will occur upon IP3 activation?

A

Activation will lead to Ca2+ mobilization from ER stores and thus degranulation

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16
Q

Activation of DAG will have what effect in mast cells?

A

This will lead to activation of PKC, which will affect transcription factors that will lead to the release of cytokines.

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17
Q

MAPK activation in the mast cells will have what effects?

A

MAPK will activate phospholipid A which will then mediate lipid mediators

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18
Q

Release of ECF-A/NCF-A by mast cells leads to what?

A

Chemotaxis for eosinophils and neutrophils

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19
Q

Release of TNF-alpha/IL-1 by mast cells leads to what?

A

ICAM-1 upregulation

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20
Q

Release of PAF by mast cells does what?

A

Aids in platelet aggregation

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21
Q

Release of heparin granules by mast cells does what?

A

This helps with anticoagulation

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22
Q

How do mast cells mediate complement activation?

A

Protease (granules) cleavage of C3a, 4a and 5a

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23
Q

IL-3 and IL-4 release by mast cells is intended for what?

A

Mast cell survival

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24
Q

IL-4, IL-5 and IL-13 by what cells in the late phase of a T1 hypersensitivity?

A

Th2 cells

25
Q

What is the role of tryptase release by mast cells?

A

Aids in mucus secretion

26
Q

What is the role of histamine in the immediate reaction during type I hypersensitivity?

A

Histamine leads to dilation of small blood vessels, increased vascular permeability, and transient contraction of smooth muscles

27
Q

What are the roles of prostaglandins in the immediate reaction?

A

Vascular dilation

28
Q

What is the role of leukotrienes in the immediate reaction of type I hypersensitivity?

A

Prolonged smooth muscle contraction

29
Q

What cytokines are released by mast cells that work in the late phase hypersensitivity?

A

TNF-alpha, IL-4 and IL-5

30
Q

What ILs work in the late phase that affect Th2 cells?

A

IL-4, 5 and 13

31
Q

What leukocytes are recruitmented in the late phase of type I hypersensitivities?

A

Neutrophils and eosinophils

32
Q

What is this an image of?

A

Mast cell

33
Q

What is this an image of?

A

Eosinophil

34
Q

Type I hypersensitivities can result in anaphylaxis, what are the symptoms of this?

A

Systemic reaction caused by widespread mast cell degranulation. Edema can lead to an airway obstruction and a fall in blood pressure can result from vascular dilation.

35
Q

What is the point of a skin test for Type I?

A

This is looking for a wheal and flare reaction on the skin. Epicutaneous skin test followed by an intradermal test

36
Q

The antigen is ragweed, does this person appear to have a hypersensitivity to ragweed? Also what are the three dots?

A

This person does have a ragweed allergy. The top is the antigen, the middle is a negative control, and the bottom is the positive control

37
Q

What is the difference between the intradermal and epicutaneous test? How does this image help explain that?

A

The intradermal skin test is more sensitive and is semiquantitative. The image shows increasing dilutions of the antigen to show a difference in immune responses.

38
Q

Why is an epicutaneous skin test done before an intradermal skin test?

A

There is a risk of anaphylaxis with the intradermal test

39
Q

What is the process of immunocap to test Type I hypersensitivity?

A

IgE from patient sample will bind to allergen covalently attached to the well. Enzyme labeled anti-IgE will be added, and then a color change will be measured to quantify how much was bound

40
Q

How would you treat anaphylaxis from a Type I hypersensitivity?

A

Epinephrine to increase cardiac output and relax airway muscles

41
Q

What would you use to treat asthma caused by a type I hypersensitivity?

A

Bronchodilators, corticosteroids to reduce inflammation, leukotriene antagonist, and histamine receptor antagonist

42
Q
A

Anti-IgG - IgG is not involved in the type I hypersensitivity reaction

43
Q

Type II hypersensitivity is characterized by?

A

Antibodies against cells or extracellular matrix proteins;

OR

Microbial antigens that cross-react with self-tissue

44
Q

What is an example of type II hypersensitivity caused by an microbial antigen?

A

Rheumatic fever caused by streptococcus

45
Q

Type II diseases with tissue injury utilizes what mechanisms?

A

Complement activation, Fc Receptor activation on neutrophils and macrophages, and opsonization of cells

46
Q

Type II diseases without tissue injury do what?

A

Antibodies with specificity for a receptor can be agonist or antagonist.

Myasthenia gravis - Blocking antibodies against the acetylcholine receptor

47
Q

How is myasthenia gravis an example of a type II disease?

A

MG blocking antibodies against the acetylcholine receptor

48
Q

How is Graves disease an example of type II disease without tissue damage?

A

Antibodies against the TSH receptor to stimulate thyroid cells

49
Q

What is a type III hypersensitivity?

A

Immune complexes deposited in vessels attract and activate leukocytes. IgG and antigen:antibody aggregates.

50
Q

What is the Arthus reaction?

A

Antigen is injected into an immune individual with IgG antibody. Local immune-complexes form. Activation on mast cells leads to degranulation leading to edema necrosis and activation of complement. Can lead to blood vessel occlusion.

51
Q

What is serum sickness?

A

Antibodies are formed to foreign proteins. Immune complexes form and are deposited in membranes, where they fix complement leading to tissue damage.

52
Q

How is post-streptococcal glomerulonephritis an example of a type III hypersensitivity?

A

Cross-reactive and anti-streptococcal antibodies can lead to nephritis

53
Q

How is systemic lupus erythematosus an example of type III hypersensitivity?

A

Antibodies against DNA and nucleoproteins leading to nephritis

54
Q

What are some treatments against type II and type III hypersensitivities?

A

Corticosteroids, IVIG, Anti-CD20 to deplete B cells, CD40 ligand (CD154) antagonists

55
Q

Type IV issue injury is mediated by?

A

CD4 T cells secreted cytokine induced inflammation. Th1 - secretes IFN gamma

Th17 secretes IL-17

56
Q

Type IV hypersensitivity is characterized by?

A

Sensitized T cells encounter antigen and then release cytokines that lead to macrophage activation and tissue damage

57
Q

What are some examples of type IV hypersensitivities?

A

TB, contact dermatitis, and some autoimmune diseases

58
Q

How is the DTH skin test different than the type I skin test?

A

This is looking for a delayed hypersensitivity in response to purified protein derivative. The type I hypersensitivity will take minutes to get a result

59
Q

How to treat type IV hypersensitivity?

A

Corticosteroids, Anti-TNF and costim blockade

Inflammation and Immunity (51 decks)

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