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Host + Defense > 4 Hypersensitivity & Allergies > Flashcards

4 Hypersensitivity & Allergies Flashcards

1
Q

Define anaphylaxis.

A

A severe, immediate, and system-wide harmful immune response to a non-pathogenic antigen
it was the first identified hypersensitivity reaction

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2
Q

Define hypersensitivity reaction.

A

an immediate or delayed immune response to innocuous antigen resulting in damage to healthy tissue

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3
Q

How many types of hypersensitivity reactions are there?

A

four

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4
Q

Which types of hypersensitivity reactions are humorally mediated?

A

Types I, II, and III

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5
Q

Type IV hypersensitivity reactions are ______ mediated.

A

cell-mediated

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6
Q

What specific antibody mediates Type I hypersensitivities?

A

IgE

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7
Q

What hypersensitivity is typically mediated by IgG?

A

Type III (forms antibody aggregates in vessels)

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8
Q

What specific part of humoral immunity mediates the Type II hypersensitivity?

A

IgG antibodies targeting non-self antigens on the surface via complement proteins (i.e. graft rejection)

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9
Q

Delayed type reaction describes what kind of hypersensitivity?

A

Type IV

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10
Q

Antigens (or allergens) that cause a Type I hypersensitivity have what characteristic(s)?

A

They’re either proteins or glycoproteins and are often times enzymatically active

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11
Q

What do enzymatically active proteins do to the body at the mucosal membrane?

A

The proteases will typically bind to pattern recognition receptors (PRRs) and activate B cells to produce IgE targeted for that protein

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12
Q

A systemic reaction to a Type I hypersensitivity presents as what?

A

anaphylactic shock

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13
Q

A type I reaction will result in what cellular response?

A

Degranulation of mast cells as well as eosinophils and basophils

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14
Q

In a Type I reaction, the antigens are presented on MHC Class II and presented to what T cell?

A

CD4 Th2 cells, which then use interleukins to activate granulocytes

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15
Q

What interleukins are used to activate mast cells during a Type I reaction?

A

Primarily IL-9 but also IL-4, IL-5, and IL-13

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16
Q

What interleukin is overly expressed to cause eosinophilia?

A

IL-5

17
Q

Name four enzymes used by mast cells to repair connective tissue.

A

Tryptase, Chymase, Cathepsin G, and Carboxypeptidase

18
Q

What do mast cells use histamine and heparin for?

A

Poison parasites, increase vascular permeability and contract smooth muscle

19
Q

What effect do mast cells have on the airway when they respond to an allergen?

A

Decrease airway diameter (smooth muscle contraction via histamine/heparin) and increase mucus secretion

20
Q

Name two enzymes used by eosinophils.

A

Peroxidase (to kill parasites/mammalian cells, and trigger histamine release from mast cells) and Collagenase (to remodel connective tissue)

21
Q

What are three toxic proteins produced and released by eosinophils?

A

Major basic protein, cationic protein, and an eosinophil-derived neurotoxin

22
Q

Why is eosinophilia bad?

A

It’s the concentration of eosinophils which degranulate their highly toxic contents and promote more inflammation

23
Q

What is the hygiene hypothesis?

A

In developed countries children aren’t exposed to as many antigens which cause their immune system to be poorly educated, leading to allergy and autoimmune disorders

24
Q

What are the two phases of allergic responses?

A

Early response which involves smooth muscle contraction, vasodilation, and fluid/mucus secretion; and Late response which involves leukocyte migration and activation

25
Q

What is hyposensitization?

A

When you have repeated exposures to escalating dosages of allergens to reduce Type I reactions

26
Q

What other therapies can be used to relieve Type I reactions?

A

Antihistamines, Leukotriene antagonist, Corticosteroids, Immunotherapeutics - all of these treat the symptoms, not the cause

27
Q

A mast cell expressing a lot of IgG4 will do what?

A

It’ll be less likely to degranulate because unlike IgE, IgG4 is an inhibitor of degranulation

28
Q

What is the effector cell in a Type II reaction?

A

CD8 T cells

29
Q

What forms in a Type III hypersensitivity reaction?

A

An aggregate of antibodies and antigens that get stuck in either the vasculature or the tissue

30
Q

What does the aggregate do in a Type III reaction?

A

The aggregate will recruit C3b complement proteins which then promote inflammation

31
Q

Is it an innate or adaptive inflammatory response in a Type III reaction?

A

Innate immune response

32
Q

What cell does most of the damage to tissue in a Type III reaction?

A

neutrophils

33
Q

Rheumatoid arthritis is an example of what type of hypersensitivity?

A

Type III

34
Q

What cells mediate Type IV reactions?

A

CD4 T cells

35
Q

Molecules causing Type IV reactions function as ________.

A

adjuvants

Host + Defense (22 decks)

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