Ch. 16 (type I hs)

Question 1

What damages the body in a hypersensitivity reaction?

Answer 1

The immune response.

Question 2

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

Answer 2

yes

Question 3

What are some examples of hypersensitivity?

Answer 3

allergic reactions

autoimmune disorders

strept kidney diseases

Question 4

What are the different types of hypersensitivity?

Answer 4

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)

Question 5

Describe type I hypersensitivity?

Answer 5

IgE mediated

leads to release of MAST cell mediators

(generally associated with allergies)

Question 6

Describe type II hypersensitivity.

Answer 6

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)

Question 7

Describe type III hypersensitivity.

Answer 7

immune complex mediated

circulating antigen/antibody complexes

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

(autoimmune)

Question 8

Describe type IV hypersensitivity.

Answer 8

CD4 cells-delayed or CD8 cell cytolysis

leads to sensitized T cells that cause cell and tissue injury

Question 9

What is type I hypersensitivity often called?

Answer 9

allergic reactions

Question 10

What are type I hypersensitivity reactions mediated by?

Answer 10

IgE

Question 11

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

Answer 11

YES

systemic - anaphylaxis

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

Question 12

Describe an allergy.

Answer 12

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

Question 13

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

Answer 13

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!

Question 14

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

Answer 14

you have a 95% chance!

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

Question 15

What is an allergen?

Answer 15

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.

Question 16

Why do allergens force eosinophils to get involved?

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

vasodilation
vascular damage
smooth muscle spasm

caused by MAST cells when they release their inflammatory mediators

Question 19

during initial exposure what cells respond during type I hypersensitivity?

Answer 19

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

Question 20

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

Answer 20

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)

Question 21

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

Answer 21

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

both eosinophils and MAST cells are responsible

Question 22

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

Answer 22

(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

Question 23

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?

Answer 23

can be 5-30 minutes.

Can last up to an hour

vasodilation, vascular leakage, smooth muscle contraction

Question 24

when does the secondary response begin in type I HS?

How long does it last?

Answer 24

Starts in 2-8 hours

Can last for days

Question 25

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

Answer 25

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

Question 26

So type I can be local or systemic?

Answer 26

Yes - local if mast cells are activated at a confined site or tissue systemic if the MAST cells are activated in the vascular system

Question 27

Is type I hypersensitivity predetermined?

Answer 27

Yes, it tends to be genetically predetermined Most individuals are allergic to more than one allergen

Question 28

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

Answer 28

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

Question 29

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

Answer 29

YES, inhalation ingestion respiratory

Question 30

What are the common food allergens?

Answer 30

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

Question 31

Do reactions to food allergies only cause gastric issues?

Answer 31

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

Question 32

Do we believe that we can outgrow allergies?

Answer 32

yes, we can become desensitized to an allergen

Question 33

Can anaphylaxis start as a local response?

Answer 33

YES

Question 34

What often causes anaphylaxis?

Answer 34

injected or ingested allergens

Question 35

is a lot of the allergen required to cause anaphylaxis?

Answer 35

NO

Question 36

What are the clinical manifestations of anaphylaxis?

Answer 36

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

Question 37

Describe the process of anaphylaxis.

Answer 37

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

Question 38

What is immunotherapy?

Answer 38

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