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Immunology > L14 Hypersensitivity and Allergy > Flashcards

L14 Hypersensitivity and Allergy Flashcards

1
Q

define type 1 hypersensitivity

A

exposure to an allergen (antigen) produces an IgE response. Mast cells bind IgE via their FceRI Fc receptor.

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2
Q

what happens when IgE binds to the allergen?

A

IgE crosslinking on mast cells, mast cell degranulation, release of mediators, brings about immediate hypersensitivity

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3
Q

examples of type 1 hypersensitivity

A

allergic rhinitis (hayfever) affecting 10% of population, eczema (atopic dermatitis), asthma, food allergies, diffuse urticaria (hives)

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4
Q

eczema (atopic dermatitis), define, immune cells involved

A

type I hypersensitivity reaction, immune cell infiltration under skin.
cytokine response is largely Th2, produces IL-4 and TNFα

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5
Q

name a drug which dampens the T cell response

A

corticosteroids which will inhibit cytokine synthesis

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6
Q

causes of urticaria (hives)

A

environmental, foods, medicines

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7
Q

what happens when an IgE is exposed to a parasite the second time?

A

triggers mast cell degranulation onto the surface of intestinal parasites

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8
Q

what cell produces IgE and what triggers its release

A

B cells and plasma cells make IgE in response to an antigenic stimulus

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9
Q

what does the presence of IL-4 and IL-13 indicate regarding class-switching of immunoglobulins?

A

they will trigger class switching from other isotypes to IgE

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10
Q

List properties of antigens

A

mainly proteins, water soluble, low Mw, Glycosylated, diverse functions, triggering immediate hypersensitivity

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11
Q

examples of allergens

A

dust mite (antigens in feces), cats (dander particles)

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12
Q

describe the wheal and flare reaction

A

inject allergen intradermally. wheal and flare will indicate IgE response if patient has been exposed to allergen previously.

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13
Q

name the MHC/HLA’s associated with allergy

A

DR2/Dw2, DR3/Dw3

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14
Q

if one of the two monozygotic twins has allergies, what is the likelihood the other twin also has it?

A

Approximately 50%

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15
Q

what percentage of Ig serum levels is typical of IgE?

A

0.001% of total serum Ig

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16
Q

Are levels of IgE elevated or decreased in allergies?

A

Elevated

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17
Q

name cell(s) and their receptor which binds IgE

A

basophils and mast cells bind IgE via their Fc receptors

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18
Q

name the different types of mast cells? (hint: think location)

A

connective tissue and mucosal (asthma) mast cells

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19
Q

name an instance where mucosal mast cells (MMCs) infiltrate the nasal epithelium.

A

hay fever patients during pollen season, bronchoalveolar fluid from lungs in asthmatics

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20
Q

what is the half life for IgE normally and what is its half-life when bound to mast cells?

A

normally 2 days, with mast cell bound is approx. 10 days.

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21
Q

what does the IgE-antigen complex crosslink with and what effect does this have?

A

cross links with the FceRI molecules on the mast cells. induces the release of mediators responsible for hypersensitivity reaction

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22
Q

percentage of asthma associated with IgE-mediated reaction and other non-immune stimuli of asthma

A

70% IgE related, other causes include drugs, cold, exercise.

23
Q

name mediators in the immune system which elicit bronchoconstriction upon inhalation of allergens?

A

histamine, leukotrienes and prostaglandins including LTD4, are spasmogens which cause bronchoconstriction.

24
Q

what effect do the spasmogens (histamine, LTD4, etc) have besides bronchconstriction?

A

induce edema, increase mucus secretion, smooth muscle constriction

25
Q

name mediators released after asthma patient inhales an allergen that cause effects other than bronchoconstriction and give their function

A

IL-5 and TNFalpha are chemotactic factors which recruit cells like eosinophils, neutrophils, lymphocytes, and macrophages from circulation.

26
Q

what impact does the inflammatory infiltrate have on the lung?

A

The inflammatory infiltrate chronically modifies the lung. effects include goblet cell hyperplasia (increased mucus), collagen deposition below the BM, and some evidence of possible smooth muscle hyperplasia.

27
Q

what can be seen in exhalation of a patient with chronically modified lungs due to asthma?

A

increased exhalation of nitric oxide.

28
Q

histopathological features of bronchial asthma

A

excess mucus, smooth muscle cell hypertrophy, submucosal inflammatory infiltration (lymphocytes and eosinophils), thickened BM.

29
Q

what is meant by a biphasic response regarding bronchial asthma?

A

initial response (immediate), later response (hours later, flat-type response, potentially more dangerous)

30
Q

effect of sodium cromoglycate on mast cells?

A

prevents mast cell degranulation and release of mediators like histamine, prostaglandins and leukotrienes. also blocks arachidonic acid

31
Q

ventolin inhalers (active ingredient, what does it treat)

A

active ingredient is salbutamol, treats bronchospasm (sudden contriction of bronchiole smooth muscle)

32
Q

beta2 agonists and asthma target and effect

A

binds beta2 receptors, blocks binding of epinephrine and norepinephrine. causes muscle relaxation and airway opening

33
Q

describe desensitization as a treatment for hypersensitivity type 1

A

regular injections of allergen extracts. progressively increase dose. small 20 aa peptides approx.
risk of anaphylactic shock, should result in gradual change from IgE production to IgG

34
Q

which T helper cell response is stronger in allergy sufferers? which interleukin does this produce?

A

Th2 cell response which produces IL-4

35
Q

IL-4 promotes the production of which immunoglobulin?

A

IgE

36
Q

are Treg cells pro or anti-inflammatory?

A

anti

37
Q

what are some anti-inflammatory cytokines?

A

IL-10 and TGF-Beta

38
Q

name the monoclonal antibody used to treat moderate-severe asthma and chronic hives, give mechanism

A

omalizumab, subcutaneous (once every 2-4 weeks), prevents IgE interaction with mast cells and its FceRI Receptor. removes ‘free IgE’

39
Q

role of IL-4

A

amplifies IgE and histmamine induced vascular endothelium dysfunction, vasodilation, and anaphylaxis.

40
Q

monoclonal antibody that targets IL-4, mechanism and what it treats

A

dupilumab, blocks IL-4 receptor which IL-13 also binds to. treats eczema, injections, can be used with topical steroids.

41
Q

non-allergic food hypersensitivity example

A

lactose - milk - tolerance

42
Q

define oral tolerance

A

oral tolerance is a state of local and systemic immune unresponsiveness that is induced by oral administration of ‘innocuous’ antigens such as food proteins.

43
Q

name the 3 immune inductive sites in the GIT

A

Peyer’s patches, mesenteric lymph nodes and lamina propria

44
Q

requirements of GALT

A

GALT must be able to:

  • digest dietary antigens without causing untoward immune reactions
  • protect the organism from pathogens.
45
Q

explain T and B cell anergy and give a cause of it

A

this is where the T&B cells have been subjected to clonal deletion and are unresponsive. caused by high doses of orally fed food antigens.

46
Q

name a cell involved in the induction of T&B cell anergy

A

dendritic cells

47
Q

what happens if T&B cell anergy is not maintained?

A

this can cause chronic GIT inflammation and hypersensitivity.

48
Q

what regulates the gut oral tolerance to dietary antigens?

A

T regulatory cells and their immunosuppressive effects stimulated by the uptake, processing and presentation of antigens in mucosal inductive sites.

49
Q

what is a way of decreasing the likelihood of childhood peanut allergy?

A

introducing peanuts early can decrease the frequency of the develpment of peanut allergy among children who are at high risk for developing the allergy.

50
Q

Systemic Lupus Erythematosus: define

A

a prototypic immune complex mediated disease, chronic, remitting and relapsing multi-system autoimmune disease.

51
Q

SLE clinical manifestations

A

predominantly women

rashes, arthritis, glomerulonephritis, thrombocytopenia, CNS involvement also seen

52
Q

characteristic features of SLE

A

auto-antibodies, often anti-nuclear (anti-DNA) antibodies as well as anti-ribonuclear proteins and anti-histones.

53
Q

how to diagnose SLE

A

serology for anti-double stranded DNA antibodies.

54
Q

MHC associated with increased risk of SLE

A

HLA-DR2, HLA-DR3

Immunology (10 decks)

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