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Pathophysiology > Ch. 16 (type I hs) > Flashcards

Ch. 16 (type I hs) Flashcards

1
Q

What damages the body in a hypersensitivity reaction?

A

The immune response.

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2
Q

Can hypersensitivity be an excessive or an inappropriate activation of the immune response?

A

yes

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3
Q

What are some examples of hypersensitivity?

A

allergic reactions

autoimmune disorders

strept kidney diseases

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4
Q

What are the different types of hypersensitivity?

A

allergy (exagerated against environmental antigens, most common)

autoimmunity (misdirected against the hosts own cells, lupus, hemolytic anemia, rheumatoid arthritis)

alloimmunity (directed against beneficial foreign tissue: blood transfusion reaction, tissue transplant rejection)

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5
Q

Describe type I hypersensitivity?

A

IgE mediated

leads to release of MAST cell mediators

(generally associated with allergies)

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6
Q

Describe type II hypersensitivity.

A

Antibody mediated

tissue specific reactions

leads to complement mediated phagocytosis, inflammation and cell injury

or leads to physiologic responses without cell injury

(like receiving the wrong type of blood)

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7
Q

Describe type III hypersensitivity.

A

immune complex mediated

circulating antigen/antibody complexes

lead to the recruitment and activation of inflammatory cells that release tissue-damaging products

(autoimmune)

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8
Q

Describe type IV hypersensitivity.

A

CD4 cells-delayed or CD8 cell cytolysis

leads to sensitized T cells that cause cell and tissue injury

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9
Q

What is type I hypersensitivity often called?

A

allergic reactions

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10
Q

What are type I hypersensitivity reactions mediated by?

A

IgE

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11
Q

Can type I hypersensitivity be local and systemic, what are some examples?

A

YES

systemic - anaphylaxis

Local or atopic - rhinitis (hay fever)
food allergies
bronchial asthma
hives
atopic dermatitis (exema)
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12
Q

Describe an allergy.

A

environmental antigens that cause an atypical immune response in genetically predisposed individuals

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13
Q

If one of your parents has allergies, exema, or asthma what is your chance of getting them?

A

you have at least a 50% chance of getting any of the three.

this means that your parents could have allergies, and you could be born with asthma!

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14
Q

What if both parents have exema, allergies, or asthma? What is the percentage of being born with one of those three then?

A

you have a 95% chance!

Remember, it doesnt have to be the same thing your parents have.

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15
Q

What is an allergen?

A

usually a foreign protein that is too large to be phagocytized (WBCs can engulf), usually they have a protective coating that makes it hard for them to be eaten as well.

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16
Q

Why do allergens force eosinophils to get involved?

A

They have to come to release their granules to break down the protective nonallergenic coat of the allergen.

THIS CAUSES THE RELEASE OF HISTAMINE FROM THE EOSINOPHILS AND THE MAST CELLS

this causes a large inflamatory response

17
Q

What happens when we are first few times exposed to an antigen that may be an allergen?

A

nothing may happen becuase the MAST cells have to be sensitized by the T cells being exposed to it, only the eosinophils are reacting at that time

18
Q

What is the early response of type I hypersensitivity and what cells are responsible for it?

A

vasodilation
vascular damage
smooth muscle spasm

caused by MAST cells when they release their inflammatory mediators

19
Q

during initial exposure what cells respond during type I hypersensitivity?

A

The eosinophils because the allergens are to large to break down. THIS PRODUCES THE late response to the allergen.

20
Q

What else is happening outside of the eosinophils response during the initial response of type I hypersensitivity?

A

The T cells are identifying the allergen and telling the B cells to make IgE antibodies that will then sensitize the MAST cells (this allows for the primary (early) response to be possible after the first few exposures)

21
Q

Describe the late response of type I hypersensitivity and the cells responsible.

A

The secondary response can cause mucosal edema, musuc secretion, leukocyte infiltration, epithelial damage, brochospasm

both eosinophils and MAST cells are responsible

22
Q

What do the MAST cells do and secrete during type I hypersensitivity reaction?

A

(lipid mediators) arachidonic acid, prostaglandins, leukotrienes, acetycholine (cause secondary response)

release cytokines that recruit and activate more inflamatory cells

release mediators responsible for primary stage

23
Q

how long after exposure does the initial/early stage of type I HS begin?

How long does it last and what are the symptoms again?

A

can be 5-30 minutes.

Can last up to an hour

vasodilation, vascular leakage, smooth muscle contraction

24
Q

when does the secondary response begin in type I HS?

How long does it last?

A

Starts in 2-8 hours

Can last for days

25
Q

What is the importance of knowing about these two phases clinically?

A

Lets say that someone comes to the ER with an allergen induced asthma attack, and you give them a breathing treatment to reverse it.

You could have gotten rid of the initial phase of that type I HS response, but there is still a chance that the secondary phase will present a few hours later on

This means that you would need to keep your eye on the patient for a while, otherwise if you send them home they could have a worse attack than the first

26
Q

So type I can be local or systemic?

A

Yes - local if mast cells are activated at a confined site or tissue

systemic if the MAST cells are activated in the vascular system

27
Q

Is type I hypersensitivity predetermined?

A

Yes, it tends to be genetically predetermined

Most individuals are allergic to more than one allergen

28
Q

Do people with type I hypersensitivity tend to have more IgE?

A

yes yes yes they also have more receptors for binding with IgE on MAST cells.

29
Q

Is how the reaction manifests usually related to the route of exposure?

A

YES,

inhalation

ingestion

respiratory

30
Q

What are the common food allergens?

A

milk, eggs, peanuts, soy, shellfish, fish, other tree nuts

31
Q

Do reactions to food allergies only cause gastric issues?

A

No, they can come out on the skin or even asthma

32
Q

Do we believe that we can outgrow allergies?

A

yes, we can become desensitized to an allergen

33
Q

Can anaphylaxis start as a local response?

A

YES

34
Q

What often causes anaphylaxis?

A

injected or ingested allergens

35
Q

is a lot of the allergen required to cause anaphylaxis?

A

NO

36
Q

What are the clinical manifestations of anaphylaxis?

A

vasodilation and bronchoconstriction

also a drop in BP because of vasodilation as well as the permeability of vessels makes vessels lose fluid

swelling of the throat

conjuntivitis

rhinitis

swollen throat

laryngeal edema

gi cramps

dysrhythmias

edema in lots of places

37
Q

Describe the process of anaphylaxis.

A

antigen enters tissues throughout the body

attaches to IgE on the surface of mast cells

mast cells degranulate which releases

acetylcholine, leukotrienes, prostaglandins, kinins, histamine

bronchial constriction => dyspnea

massive vasodilation => peripheral resistance decreases (edema) => decrease in blood pressure

Increase capillary permeability => exudate leaves blood (edema) => decreased blood volume => blood pressure decreases

38
Q

What is immunotherapy?

A

These are allergy shots that desensitize our immune cells by turning down the response to the antigen

this makes the WBCs produce less IgE

Next exposure to the antigen leads to a less severe reactions with smaller manifestations

This doesnt treat the symptoms like antihistamines, it actually treats the cause

Pathophysiology (13 decks)

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