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Host Defense Exam 2 > IgE Immunology > Flashcards

IgE Immunology Flashcards

1
Q

What is type I hypersensitivity disease and what is it mediated by?

A

Allergic responses, mediated by IgE

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2
Q

What is type II hypersensitivity disease and what is it mediated by?

A

Ab directed against tissue antigens, mediated by IgG

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3
Q

What is type III hypersensitivity disease and what is it mediated by?

A

Immune complex mediated disease, mediated by Ag + IgG

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4
Q

What is type IV hypersensitivity disease and what is it mediated by?

A

Delayed hypersensitivity disease, mediated by T cells

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5
Q

What cells are most responsible for allergic symptoms?

A

Eosinophils, mast cells, basophils

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6
Q

define allergy

A

a disease induced by a reaction to a usually innocuousAg

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7
Q

Define atopy

A

genetic predisposition to develop IgE antibodies upon exposure to environmental allergens

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8
Q

What cells does IgE interact with?

A

Mast cells and basophils have high affinity Fc-epsilon-R that can bind the Fc region of IgE

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9
Q

What do mast cells and basophils have in their cytoplasm?

A

histamine, TNF-alpha, leukotrienes

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10
Q

What are the toxic mediators of mast cells?

A

histamine and heparin

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11
Q

What are the lipid mediators of mast cells?

A

leukotrienes - LTC4, LTD4, LTE4

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12
Q

What enzymes do mast cells contain?

A

Tryptase, chymase, cathepsin G, carboxypeptidase

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13
Q

What cytokines do mast cells release?

A

IL-4, IL-13, IL-3, IL-5, GM-CSF, TNF-alpha

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14
Q

What chemokines do mast cells release?

A

MIP-1a

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15
Q

what are the two types of mast cells?

A

MC(t): tryptase

Skin MC(tc): tryptase and chymase

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16
Q

What is a characteristic of many allergens?

A

they contain chitin – a polysaccharide not found in humans

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17
Q

What can induce an allergic response in an atopic individual?

A

almost any protein

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18
Q

if two parents are atopic, what is the chance their children ill be atopic?

A

50%

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19
Q

What are basophils?

A

circulating leukocytes

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20
Q

Where are MC(t) cells found?

A

prominent mast cell type within the mucosa of the respiratory and gastrointestinal tracts and increase with mucosal inflammation

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21
Q

Where are MC(tc) cells found?

A

localized within connective tissues, such as the dermis, submucosa of the gastrointestinal tract, heart, conjunctivae, and perivascular tissues

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22
Q

What MHC class are the immunodominant peptides of allergens presented by?

A

Class II D MHC of dendritic cells

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23
Q

What do the D and non-MHC genes do?

A

promote IgE production over IgG responses by influencing the type of TLR activated, type of T-helper cell and cytokine milieu present during allergen presentation by APC

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24
Q

what is the relationship between atopy, serum levels of IgE, and allergic reactions?

A

direct relationship

25
Q

What are some examples of genes that can influence the allergic response?

A

varying expression of IFN-γ via the T-Bet gene, FcεR avidity via a maternal gene, IgE synthesis and bronchial reactivity, IL-13 synthesis

26
Q

How is MHC involved in the allergic response?

A

Different MHC-II will present different peptides that differ in their antigenic potency

27
Q

Almost anything can be an allergen. However, what is the trend towards?

A

proteins with enzymatic activity

28
Q

How is timing important in developing allergies?

A

decreased early exposure to infections in the genetically predisposed individual is associated with insufficient T regulator control of IgE

29
Q

what kind of route predominates in an allergic response?

A

mucosal

30
Q

Discuss the chain of events that leads to an allergic response

A

Allergen crosses mucosal epithelia and is taken up by dendritic cell

dendritic cell presents to a B cell in the lymph nodes and a Th2 cell prompts switching of B cell to IgE production

plasma cell releases Ab specific for the Ag at the site of entry

IgE binds to Fc-epsilon-RI on mast cell, and upon Ag binding, leads to the release of mast cell granules which cause allergic symptoms

31
Q

What is the only FcR that can be occupied by Ab without antigen?

A

Fc-epsilon-R

Fc-e-RI has a relative binding strength of 20,000x

32
Q

What is the temporal sequence of mast cell release?

A

histamines and prostaglandins are released within seconds of IgE cross linking

leukotrienes are released 10-15 minutes later

33
Q

What is the early phase of an allergic reaction?

A

within 15 minutes prostaglandin and leukotriene release and direct complement activation

34
Q

Can the early phase occur if there has not been a previous exposure?

A

No!

35
Q

What is the late phase of an allergic reaction dependent upon?

A

completely dependent on Th2

36
Q

What cytokines are released in the late phase of an allergic reaction?

A

IL3, 4, 5, 10, 13

37
Q

What is the late phase of an allergic reaction characterized by?

A

Eosinophils

38
Q

What is the clinical manifestation of an allergic response dependent upon?

A

The site of reaction

39
Q

What is the main organ and route of entry for anaphylaxis?

A

systemic

Stings, Ingestion, Inhalation(rare)

40
Q

What are the typical allergens and main symptoms of anaphylaxis?

A

insect venom, drugs, food

shock, hypotension, wheezing, urticaria, angioedema

41
Q

What is the main organ and route of entry for Eczema (atopic dermatitis), Urticaria, and Angioedema?

A

Skin and other various organs

contact, ingestion, inhalation (rare)

42
Q

What are the typical allergens and main symptoms of Eczema (atopic dermatitis), Urticaria, and Angioedema?

A

uncertain, various foods, drugs

Pruritic, vesicular, and swollen lesions

43
Q

What is the main organ and route of entry for Allergic Rhinitis and Conjunctivitis?

A

Nose and eyes

contact with mucous membrane

44
Q

What are the typical allergens and main symptoms of Allergic Rhinitis and Conjunctivitis?

A

Pollens, dust mites, animal dander, molds

Runny nose, redness and itching of eyes

45
Q

What is the main organ and route of entry for asthma?

A

Lungs

inhalation

46
Q

What are the typical allergens and main symptoms of asthma?

A

Pollens, dust mites, animal dander, molds

Wheezing, dyspnea, tachypnea

47
Q

What is the main organ and route of entry for Allergic gastroenteropathy?

A

Gastro-intestinal tract

ingestion

48
Q

What are the typical allergens and main symptoms of alleric gastroenteropathy?

A

various foods

Pain, bloating, vomiting, diarrhea

49
Q

What is the result of a high dose intravenous allergen?

A

general histamine release by connective tissue mast cells, which acts on blood vessels to increase permeability, leading to systemic anaphylactic shock

50
Q

what is the result of a low dose subcutaneous allergen?

A

local histamine release by connective tissue mast cells causing wheal and flare reactions

51
Q

What is the result of low dose inhaled allergen?

A

allergic rhinitis (upper airway) caused by increased mucous production and nasal irritation

asthma (lower airway) due to contraction of bronchial smooth muscle and increased mucous production

52
Q

What is the result of ingestion of an allergen?

A

contraction of intestinal smooth muscle leads to vomiting

outflow of fluid into the gut causes diarrhea

antigen diffuses into the blood stream causing urticaria, anaphylaxis, or atopic eczema

53
Q

How do you test for allergen in people?

A

in-vivo - skin testing

in vitro - RAST

54
Q

What is the positive control in a skin test?

A

histamine

55
Q

How do you do the RAST assay?

A

add pt serum to a cellulose disc with covalently bound allergen

IgE present in serum will bind to allergen

wash, add radio-labeled anti-IgE, measure

56
Q

How would you mitigate the effects of the allergic mediators?

A

antihistamines, beta blockers, lipoxygenase inhibitors

57
Q

How would you treat chronic inflammatory reactions?

A

general anti-inflammatory effects via corticosteroids

58
Q

how would you treat the Th2 response of an allergic reaction?

A

induction of Tregs, desensitization by injection of specific Ag

59
Q

how would you prevent IgE binding to the mast cell?

A

Anti-IgE Ab would bind to Fc region and prevent binding to Fc receptor

Host Defense Exam 2 (11 decks)

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