Exam 2- Type I Hypersensitivity

Question 1

what is an inflammatory response that causes extensive damage to the host’s tissues, even death, called?

Answer 1

hypersensitivity or allergy

Question 2

IgE-mediated type I hypersensitivity (immediate hypersensitivity) is caused by coming into contact with an antigen against which the host has ________________________

Answer 2

pre-existing IgE antibodies

Question 3

where are high affinity Fc-epsilon-RI receptors found?

Answer 3

mast cells, basophils, and eosinophils

Question 4

true/false: allergens are typically presented to the immune system as high doses

Answer 4

false: very low doses

Question 5

which Th cell response is required to induce type I hypersensitivity reactions?

Answer 5

Th2

Question 6

what do mast cell granules do?

Answer 6

potent mediators immediate hypersensitivity reactions

Question 7

how are mast cells, basophils, and eosinophils activated once the IgE molecule is bound?

Answer 7

cross-linking of the Fc-epsilon-RI receptors

Question 8

what are the primary and secondary mediators?

Answer 8

primary: pre-formed and stored in granules, immediate hypersensitivity
secondary: synthesized after or released by enzymatic breakdown of cell membrane phospholipids during degranulation process

Question 9

is histamine short-lived or long-lived?

Answer 9

short-lived

Question 10

is the genetic predisposition to develop Type I hypersensitivity multigenic?

Answer 10

yes

Question 11

true/false: the majority of IgE in the body is present in blood

Answer 11

false

Question 12

true/false: mast cells of non-allergic individuals have IgE antibodies bound to the surface of their mast cells

Answer 12

true

Question 13

what are the phases of type I hypersensitivity?

Answer 13

sensitization phase
activation phase
effector phase

Question 14

what does the “wheal and flare reaction” show?

Answer 14

locally dilated blood vessels engorged with red blood cells

Question 15

what does the late phase reaction of type I hypersensitivity consist of?

Answer 15

accumulation of inflammatory leukocytes

Question 16

what inhibits the late phase of type I hypersensitivity reactions (rich in eosinophils)?

Answer 16

corticosteroids, not antihistamines

Question 17

what is allergic rhinitis?

Answer 17

airborne antigens react with IgE-sensitized mast cells in nasal passages and conjunctiva

Question 18

what is system anaphylaxis or anaphylactic shock caused by?

Answer 18

systemic release vasoactive mediators (mainly histamine and leukotrienes)

Question 19

what are the two antibody based tests for diagnosis of allergies?

Answer 19

radioallergosorbent test (RAST)
ELISA

Question 20

what classes of drugs are given for therapy for allergies?

Answer 20

antihistamines
antileukotrienes
corticosteroids
epinephrine
cytopoint

Question 21

how does allergen immunotherapy work?

Answer 21

shift towards allergen-specific IgG production
shift to Treg subset which suppressed Th2 response

Question 22

what is the principle protective function of IgE-mediated immune reactions?

Answer 22

readication of parasitic worms such as helminths

Question 23

what do eosinophils release in response to their Fc-epsilon-RI receptors binding to IgE and cross-linking?

Answer 23

major basic protein (MBP)

Question 24

true/false: allergy shots lead to induced Treg response against the allergen used in the shots

Answer 24

true

Question 25

where is most of the IgE in the body?

Answer 25

bound to Fc receptor Fc-epsilon-RI on mast cells, basophils, and eosinophils

Question 26

what is the sequence of events for immediate hypersensitivity?

Answer 26

antigen exposure activation Th2 cells for the antigen cytokine help from Th2 cells to B cells class switching to IgE production IgE IgE binds to Fc receptors on mast cells re-exposure of antigen

Question 27

what does it mean that allergens are multivalent?

Answer 27

have one or more epitopes that are repetitive, and IgE response mounted against those epitopes

Question 28

what cytokines do Th2 cells produce?

Answer 28

IL-4, IL-5, IL-13

Question 29

what does the cytokine IL-4 do?

Answer 29

helps allergen-specific B cells class-switch to IgE

Question 30

what does the cytokine IL-5 do?

Answer 30

activates eosinophils- common in many immediate hypersensitivity reactions

Question 31

what does the cytokine IL-13 do?

Answer 31

stimulates epithelial cells to secrete increased amounts of mucus

Question 32

what cytokine is significantly higher in severely allergic individuals?

Answer 32

IL-4

Question 33

how are mast cells and basophils activated by IgE?

Answer 33

cross-linking of the Fc-epsilon-RI receptors

Question 34

what is the difference between primary and secondary mediators in hypersensitivity reactions?

Answer 34

primary: pre-made and released immediately: immediate hypersensitivity secondary: synthesized or released by enzymatic breakdown of cell membrane phospholipids during degranulation process

Question 35

are histamine's actions short-lived or long-lived?

Answer 35

short-lived because it is rapidly catabolized

Question 36

what are the actions of histamine?

Answer 36

leakage plasma into tissues vasodilation increased peristalsis and bronchospasms

Question 37

what are the actions of prostaglandins?

Answer 37

vasodilation bronchoconstriction

Question 38

is histamine stronger acting than leukotrienes?

Answer 38

no, leukotrienes are much stronger and longer lasting more potent bronchoconstrictors and stimulators of vascular permeability and mucus secretion

Question 39

what are important cytokines that mast cells produce in hypersensitivity?

Answer 39

TNF-alpha: inflammation IL-4: Th2 response

Question 40

what causes the late phase reaction after the wheal and flare reaction (2-6 hours)?

Answer 40

accumulation inflammatory leukocytes: neutrophils, eosinophils, basophils, and CD4+ Th2 cells

Question 41

true/false: the late phase reaction is rich in eosinophils

Answer 41

true

Question 42

chronic inflammation in asthma is associated with increased presence of ___________, ___________, ___________, and _____________

Answer 42

lymphocytes eosinophils neutrophils other leukocytes

Question 43

what is the difference in food allergies and food intolerances in presenting signs?

Answer 43

food allergies: itching and skin problems food intolerances: diarrhea or vomiting

Question 44

what is in the cutaneous inflammatory infiltrate in dermatitis?

Answer 44

mast cells dendritic cells low numbers eosinophils and neutrophils

Question 45

what are the main vasoactive mediators released in systemic anaphylaxis?

Answer 45

histamine and leukotrienes

Question 46

what are the two antibody based tests for diagnosis of type I hypersensitivity?

Answer 46

radioallergosorbent test ELISA