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Micro and Immunology > Allergic diseases > Flashcards

Allergic diseases Flashcards

1
Q

Allergy is the production of ____ antibodies in response to a _______ antigen.

A

IgE

protein

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2
Q

The allergic condition is called ______.

A

Atopy

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3
Q

What kind of reaction is an allergic reaction?

A

Type 1 hypersensitivity reaction

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4
Q

Harmless environmental antigen

A

Allergen

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5
Q

What are the most common symptoms of allergic reactions?

A

Asthma
Hay fever (allergic rhinitis)
Eczema (atopic dermatitis)

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6
Q

People with one atopic condition are more likely to develop what?

A

Another atopic condition

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7
Q

What is the atopic triad?

A 
Most common symptoms of an allergic reaction.
Includes:
Asthma
Hay fever (allergic rhinitis)
Eczema (atopic dermatitis)
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8
Q

Many allergies start in ______.

A

children

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9
Q

Symptoms of allergies in children typically manifest as what at the beginning?

A

Eczema or a food allergy

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10
Q

Allergies tend to start first on the _____ or in the ____ tract. As one ages, this will switch to affect the ________ tract, instead.

A

skin
GI
respiratory

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11
Q

What is the general transition in symptoms for allergies?

A

From food allergy or atopic dermatitis, to astham or allergic rhinitis.

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12
Q

Which tends to disappear faster, Food allergies or Atopic dermatitis?

A

Food allergies

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13
Q

What is the first exposure or primary immune response called in allergies?

A

Sensitization

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14
Q

Describe the symptoms of sensitization.

A

Absent or mild

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15
Q

What B cell types are made during sensitization?

A

Long-lived plasma cells that secrete IgE antibodies

Memory IgE+ B cells

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16
Q

What T cell is needed for the allergic response?

A

effector Th 2 cell

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17
Q

What generates the effector Th2 cell?

A

Dendritic cell takes up allergen, migrates to secondary lymphoid tissue and presents antigenic peptides on MHC 2 to activate native Th cell.
Naive Th cell is told by the dendritic cell to become a Th2 cell.

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18
Q

Which cell tells the B cells in allergies to undergo class switching to IgE class?

A

effector Th2 cell

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19
Q

Describe (pathway) sensitization.

A

Allergen enters the body.
Subepithelial dendritic cell takes up allergen, leaves tissue and migrates to secondary lymphoid tissue
Presents allergen on MHC class II to naive Th cell.
DC secretes cytokines telling naive Th cell to become an effector Th2 cell.
Meanwhile, B cell has bound allergen and presents it on MHC class II to effector TH2 cell
Th2 cell secretes cytokines to cause class switching to Ige
B cell undergoes clonal expansion, get production of IgE against allergen and get IgE+ memory cells
(all of this occurs in secondary lymphoid tissue)

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20
Q

Mast cells express _____ that binds IgE antibodies.

A

Fc receptor

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21
Q

On a sensitized person, what is bound to mast cells?

A

allergen-specific IgE antibodies

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22
Q

How do IgE antibodies reach mast cells?

A

Mast cells are in the tissues; IgE antibodies return to the tissues and bind to them.

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23
Q

Where are mast cells abundant?

A

In all tissues

24
Q

What do mast cells contain?

A

Many cytoplasmic granules that contain histamine

25
Q

Re-exposure to the same allergen leads to what?

A

memory response

26
Q

The memory response is quite different from the sensitization in that there is appearance of _______.

A

symptoms

27
Q

What happens, with mast cells, during the memory response?

A

Allergen enters body again.
Mast cells with bound allergen-specific IgE Abs bind to allergen.
This activates the mast cell, which secretes pro-inflammatory cytokines and chemokines and it degranulates - releasing histamine into the tissue

28
Q

How quick is the activation of mast cells?

A

Occurs within minutes

29
Q

What are the outcomes of mast cell activation?

A

Release of pro-inflammatory cytokines and chemokines
Pro-inflammatory cytokines activate endothelial cells which leads to inflammation
Histamine binds to histamine receptors on:
goblet cells –> secrete mucus
Nerves –> sneezing
Smooth muscle cells –> contraction

30
Q

When pro-inflammatory cytokines are released by mast cells, this causes inflammation. What are the different things that occur in inflammation?

A

Vasodilation and increased permeability
Nasal congestion
More anti-pollen IgE Abs enter the tissue
Eosinophils enter the tissue

31
Q

What is the late phase of inflammation for allergies?

A

Proteins and cells can enter the tissue - i.e. more anti-allergen IgE enters the tissue & eosinophils enter the tissue

32
Q

Early phase inflammation is due to what?

A

Activation of mast cells - degranulation and cytokine release

33
Q

What is late phase inflammation?

A

Widespread inflammation due to cellular infiltration –> tissue damage

34
Q

Tissue damage in allergy is due to what?

A

Infiltrating eosinophils

35
Q

Eosinophils:

  • _______ recruit eosinophils into inflammed tissue
  • ____________ activate eosinophils to degranulate
  • release highly _____ molecules –> _____ cells
A

Chemokines
pro-inflammatory cytokines
toxic
kill

36
Q

How many eosinophils are usually in the tissues?

A

Very few since they are toxic

37
Q

What kind of cells are killed by eosinophils?

A

Any cell in the tissue

38
Q

Allergic rhinitis

  • allergen inhaled into the ______ respiratory tract
  • activates mast cells in the ______ passage
A

upper

nasal

39
Q

Describe the process of hay fever.

A

Mast cells with IgE in nasal passage.
Allergen inhaled and binds to mast cells causing them to degranulate and release cytokines and histamine.
Histamine causes lots of mucus to be secreted.
Later on, eosinophils enter the tissues.
Also, plasma gets into the tissues, causing swelling. (this is the reason for a runny nose)

40
Q

Asthma:

- allergen enters the _____ respiratory tract

A

lower (and upper as well)

41
Q

Describe the process of asthma.

A

Mast cell with IgE binds to allergen in the lower respiratory tract
Get mast cell degranulation, inflammation, mucus secretion in the LRT
Smooth muscle in the LRT contracts in response to histamine - broncospasms
in late stage, get widespread inflammation and eosinophils entering and causing tissue damage

42
Q

Route of entry = inhalation.

Provide the site of attack, allergic reaction and response.

A

Site of attack = respiratory tract
Upper –> overproduction of mucus –> rhinitis
lower tract –> bronchoconstriction –> asthma

43
Q

Route of entry = injection

Provide the site of attack, allergic reaction and response.

A

Site of attack:
skin –> local inflammation –> wheal and flare reaction
Bloodstream –> systemic inflammation —> anaphylaxis

44
Q

Route of entry = ingestion

Provide the site of attack, allergic reaction and response.

A

Site of attack:
GI tract –> intestinal smooth muscle constriction –> gastroenteritis (vomit, diarrhea)
can also enter blood if absorbed rapidly –> anaphylaxis

45
Q

Severe, potentially life-threatening allergic reaction that requires immediate attention.

A

Anaphylaxis

46
Q

Anaphylaxis is provoked by what?

A

Any allergen that enters the bloodstream (injected directly into blood or absorbed rapidly in gut)

47
Q

How is anaphylaxis systemic?

A

Circulating allergen (and IgE antibodies) can enter all tissues, activate all mast cells resulting in inflammation and widespread muscle constriction

48
Q

How is low blood pressure achieved during anaphyalxis?

A

Due to inflammation, get increased permeability systemically causing fluid and plasma to leak into tissues, lowering blood pressure.

49
Q

What is anaphylactic shock?

A

Extreme drop in BP due to extensive fluid loss from blood vessels

50
Q

How is anaphylactic shock temporarily controlled?

A

Through administration of epinephrine through an epipen

51
Q

How does epinephrine combat anaphylactic shock?

A

Epinephrine rapidly increases BP by causing systemic vasoconstriction and relaxing smooth muscle cells

52
Q

Vast majority of cases of anaphylaxis are due to what types of allergens?

A

Food allergens

53
Q

What are the different treatments for anaphylaxis?

A

Minimize exposure to the allergen
Block effector responses: (e.g. anti-histamines, inhibit degranulation, relax bronchial smooth muscle, [corticosteroids as anti-inflammatory for late-phase reaction]
Allergy shots

54
Q

What is the principle of allergy shots?

A

Divert immune response from IgE to IgG

55
Q

What are the target cells of allergy shots?

How does it work?

A

Target cells are Th2 cells, want to convert to Tfh cell response.
Tfh cytokines induce IgG, rather than IgE.

56
Q

How are allergies diagnosed?

A

Serum IgE levels (high during allergy)

Skin prick test

57
Q

How does a skin prick test work?

A

Inject small quantities of common allergens subcutaneously.
Allergens to which the person is allergic shows local inflammation withinn minutes at the injection site - wheal and flare reaction

Micro and Immunology (38 decks)

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