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Infection and immunity 2 > Hypersensitivity > Flashcards

Hypersensitivity Flashcards

1
Q

give some common sources of allergens

  • inhaled
  • injected
A

inhaled materials

  • plant pollens
  • mold spores
  • dander of domesticated animals
  • faces of v small animals e.g. house dust mites

injected materials

  • insect venoms
  • vaccines
  • drugs
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2
Q

give some common sources of allergens

  • ingested
  • contacted
A

ingested

  • food e.g. peanuts
  • orally administered drugs

contacted

  • plant leaves e.g. poison ivy
  • metals e.g. nickel
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3
Q

what are the 1st 2 types of hypersensitivity reactions?

A

type 1

  • binding of antigen to IgE on mast cells
  • release of inflammatory mediators

type 2
- small molecules that modify cell-surface components perceived as foreign by immune system

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4
Q

what are the type 3 and 4 hypersensitivity reactions?

A

type 3

  • small soluble immune complexes
  • small soluble molecules + IgG deposited in the walls of small blood vessels or alveoli of the lungs

type 4
- products of antigen-specific effector T-cells CD4 Th1 cells

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5
Q

Type 1:

what is the immune reactant?

what is the antigen?

what is the effector mechanism?

what are the examples of hypersensitivity reactions?

A

IgE

soluble antigen

mast-cell activation

allergic rhinitis
asthma
systemic anaphylaxis

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6
Q

Type 2:

what is the immune reactant?

what is the antigen?

what is the effector mechanism?

what are the examples of hypersensitivity reactions?

A

IgG

  1. cell- or matrix- associated antigen
    OR 2. cell-surface receptor
  2. complement, FcR+ cells
  3. antibody alters signalling
  4. some drug allergies e.g. penicillin
  5. chronic urticaria
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7
Q

type 3

what is the immune reactant?

what is the antigen?

what are the effector mechanisms?

what are the examples of hypersensitivity reactions?

A

IgG

soluble antigen

complement
phagocytes

serum sickness
arthus reaction

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8
Q

type 4

what are the immune reactants?

what are the antigens?

what are the effector mechanisms?

what are the examples of hypersensitivity reactions?

A
  1. Th1 cells
  2. Th2 cells
  3. CTL

1 + 2. soluble antigen
3. cell-associated antigen

  1. macrophage activation
  2. eosinophil activation
  3. cytotoxicity

1 + 3. contact dermatitis
2. chronic asthma or chronic allergic rhinitis

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9
Q

describe the process of type 1 hypersensitivity

A
  1. allergen binds and turns B cells into plasma cells that produce lots of IgE
  2. IgE binds to cells with IgE receptors on
    = mast cells
  3. mast cells filled with granules containing inflammatory mediators
  4. allergen cross-links with bound IgE on mast cell surface
  5. -> de-granulation of mast cell granules and release of inflammatory mediators
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10
Q

where are mast cells found?

A

mucosal and epithelial tissues

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11
Q

what is histamine?

what is its role?

A

toxic mediator in mast cell granules

toxic to parasites
increases vascular permeability
causes smooth muscle contraction

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12
Q

what are Leukotrienes C4 and D4?

what is their function?

what drug can inhibit them?

A

lipid mediators in mast cell granules

inflammation
smooth muscle contraction
increased vascular permeability
mucus secretion

aspirin
(anti-inflammatory)

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13
Q

where are histamine receptors?

A

H1 endothelial cells

smooth muscle cells

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14
Q

how do you prevent and treat allergic reactions?

A

prevent:
avoiding contact with the allergen

treatment:
drugs 
- antihistamines, corticosteroids
immunological 
- desensitisation
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15
Q

describe how desensitisation works

A

monoclonal antibody binds to IgE

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16
Q

describe how desensitisation works

A

monoclonal antibody binds to IgE
-> prevents IgE binding to receptor on mast cell

(works the same for Fc)

17
Q

why do we have type 1 hypersensitivity?

how does it do this?

A

part of immune system specialised to fight worm infection

gastrointestinal tract:
increases peristalsis and muscle contractions
increased fluid secretion
-> expulsion via vomit or diarrhoea

airways:
decreases diameter
produces more mucous
-> expulsion via phlegm or coughing

blood vessels:
increased blood flow
increased permeability
-> increased lymph flow and carriage of antigen to lymph nodes

18
Q

give an example of types of worms which can still effect people today

A

Guinea worm
- drinking water contaminated by larvae

Toxocara canis
- from dog faeces

19
Q

what do Helminth infections stimulate?

A

CD4 Th2-like receptors
-> raised levels of IgE + increased no.s of eosinophils

also:

  • down regulates Th1 immune responses
  • protects against allergies
20
Q

what is the Th1-Th2 balance?

what are their different roles?

A

the balance between different T helper cells

Th1

  • activation of macrophages, cytotoxic T cells, NK cells
  • elimination of cellular antigens (viruses, intracellular bacteria, tumour cells)

Th2

  • stimulation of B cells
  • boost in the synthesis of IgE, IgG1 and IgG3 antibodies
21
Q

what happens if the Th1-Th2 balance is unbalanced?

A

more Th1
= immune response
-> can lead to autoimmunity

more Th2
= allergic response

22
Q

how do helminth infections effect the Th1-Th2 balance?

A

induce strong Th2 responses

but also protect against allergy

23
Q

what inhibitory responses can Helminth infections have?

A

blood circulation

pancreas

lungs

CNS

24
Q

how do helminths suppress autoimmunity and allergy?

A

via type 2 or regulatory immune response

different immunomodulatory molecules (IMs) activate immune cells that promote responses

25
Q

what is the hygiene/old friends hypothesis?

A

increased hygiene and lack of exposure to microbes have affected our immune system
-> resulting in development of certain diseases

26
Q

what factors favour the Th1 phenotype (non-allergic response)?

A

presence of older siblings

early exposure to day care

TB, measles, hep A infection

rural environment

27
Q

what factors favour the Th2 phenotype (allergic response)?

A

widespread use of ABs

western lifestyle

urban environment

diet

sensitisation to house-dust mites and cockroaches

28
Q

what did Joel Weinstock suggest?

A

the failure to acquire helminthic parasites could predispose to crohn’s disease

in a study:
21/29 patients went into complete remission after ingesting T.suis eggs

Infection and immunity 2 (13 decks)

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