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*Haematology + Immunology > Immunology 3 - Hypersensitivity > Flashcards

Immunology 3 - Hypersensitivity Flashcards

1
Q

What are CD8+ cells?

A

T killer cells

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2
Q

What are CD4+ cells?

A

T helper cells

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3
Q

What is Type 1 hypersensitivity reaction?

A

Allergy/immediate hypersensitivity

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4
Q

Allergies are mediated by what?

A

IgE

Hypersensitive T helper cells

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5
Q

What are the phases of type 1 hypersensitivity?

A

Sensitisation Phase

Reaction phase

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6
Q

What is the atopic triad?

A

Atopic dermatitis
Atopic asthma
Allergic rhinitis

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7
Q

What is atopic dermatitis?

A

Eczema

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8
Q

What is the pathophysiology of atopic dermatitis?

A

Degranlation of basophils + mast cells in response to sensitised IgE
“leaky” skin lets allergen in and water out

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9
Q

How are allergies investigaed?

A

Skin testing
Patch testing
Serum Tryptase

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10
Q

How are allergies treated?

A

Antihistamines
Corticosteroids
Adrenaline
Allergen avoidance

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11
Q

What blood antibodies do type A blood individuals have in their plasma?

A

Anti B

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12
Q

What blood antibodies do type O blood individuals have in their plasma?

A

Anti-A and anti-B

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13
Q

What is a hypersensitivity reaction?

A

Excessive immune response to an antigen that causes harm

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14
Q

What pathogens are associated with hypersensitivity reactions?

A

Influenza - cytokine storm

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15
Q

How does Influenza cause hypersensitivity reaction?

A

Cytokine storm
Cytokines attract leukocytes and trigger vascular changes
Hypotension and coagulation
Cytokines can spill into systemic circulation

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16
Q

How can dust trigger hypersensitivity?

A

Dust can mimic parasites and stimulate an antibody response

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17
Q

How do small molecules trigger hypersensitivity?

A

Act as haptens - bind to proteins and elicit immune response

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18
Q

Type 1 hypersensitivity is mediated by what?

A

Immediate response by IgE

Mast cells, Eosinophil degranulation

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19
Q

What is a Type 2 hypersensitivity reaction?

A

Previous exposure causing antibody generation

Reaction on SECOND exposure

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20
Q

What is a Type 3 hypersensitivity reaction?

A

Immune complex

Like type 2 but takes hrs

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21
Q

What is a Type 4 hypersensitivity reaction?

A

2-3 day delayed hypersensitivity

- autoimmunity associated

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22
Q

Type 2 hypersensitivity is mediated by what?

A

IgG

Complement, phagocytes

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23
Q

Type 3 hypersensitivity is mediated by what?

A

IgG

Complement, neutrophils

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24
Q

Type 4 hypersensitivity is mediated by what?

A

T-cells

Macrophages

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25
Q

Outline the pathway of Type 1 hypersensitivity

A

Th2 cells release IL-4
IL4 stimulates B-cells to release IgE
IgE binds to the allergen

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26
Q

What are the typical atopic symptoms?

A 
Anaphylaxis
Angioedema 
Urticaria 
Rhinitis
Asthma
Eczema
27
Q

Peanut allergy is associated with which proteins?

A

Ara h2 - stable protein

Ara h8 - unstable

28
Q

Which peanut protein is associated with cross-reactivity?

A

Ara h8

29
Q

What allergen is associated with penicillin?

A

beta-lactam

30
Q

What is the role of filaggrin in allergies?

A

Expressed by keratinocytes
Maintains epithelial barriers (moisture and pH)
Polymorphisms in Filaggrin associated with allergy

31
Q

How does the time of allergy development affect allergies?

A

Developing an allergy whilst young increases the risk of developing another

32
Q

What is the hygiene hypothesis?

A

Increase in allergies in developing world caused by reduced early exposure to microorganisms

33
Q

Outline anaphylaxis?

A

Mast cells produce prostaglandins and leukotrienes
This causes vasodilation and vascular permeability
Fluids shift from vascular to extravascular space
This causes a severe BP drop
Histamine release in skin causes swelling

34
Q

What pathways of mast cells cause prostaglandin and leukotriene release?

A

Cyclooxygenase

Lipoxygenase

35
Q

Outline Allergic rhinitis

A

Allergens stimulate mast cells in nasal mucosa
Vasodilation and oedema causes nasal stuffiness
Leukotrienes cause mucus secretion

36
Q

What is the affect of leukotrienes on the lungs?

A

Smooth muscle contraction leading to reduced airflow

This causes wheeze

37
Q

How are allergies treated?

A 
Desensitisation (immunotherapy)
B2-adrenergic agonists
Epinephrine
Antihistamines 
Anto-leukotrienes
Corticosteroids
38
Q

How do B2-adrenergic agonists work?

A

(salbutamol)

Prevents bronchial smooth muscle contraction

39
Q

How does Epinephrine work?

A

Stimlates alpha and beta adrenergic receptors

Increase blood pressure and decrease vascular permeability

40
Q

How do antihistamines work?

A

Block histamine receptors in skin, nose and mucus membranes

41
Q

What is Type 2 hypersensitivity?

A

Antibody mediated hypersensitivity
IgG or IgM reacting with antigen on cell surface
Causes immune mediated haemolysis

42
Q

Anti B and Anti A antibodies are which type of antibodies?

A

IgM

43
Q

What is Alloimmune haemolysis?

A

Rhesus antigen

IgG crosses placenta and causes haemolytic disease in SECOND child

44
Q

What are the main types of Immune mediated haemolysis?

A

Autoimmune
Alloimmune
Type 2 autoimmune

45
Q

What is Goodpasture’s syndrome?

A

Type II Autoimmune Hypersensitivity Against Solid Tissue

IgG autoantibodies bind to long and glomeruli - inflammatory response

46
Q

What is the mechanisms of penicillin allergy?

A

Penicillin binds to proteins on RBC surface - acts as hapten
Causes that RBC to be destroyed by FcR on splenic macrophage

47
Q

What mutation is associated with Graves Disease?

A

HLA allele DR3

48
Q

What is Type 3 hypersensitivity?

A

Immune complex disease - take time to form

IgG mediated

49
Q

What is required for antigens to form complexes?

A

Antigens must be polyvalent

Ratio of antibodies:antigens is vital

50
Q

How are complexes cleared?

A

Complement Receptor 1 transfers complexes to phagocytes

51
Q

Failure of complex clearance leads to what?

A

Activation of the innate immune system (mast cells and platelets)

52
Q

What is Immune complex disease of the kidney?

A

Glomerulonephriits - immune complexes form in epithelial lining causing infiltrate

53
Q

What are the mechanisms for immune damage of the glomerulus?

A

Autoantibodies against the glomerular basement membrane (Goodpasture’s)
Immune complex deposits in the glomerulus (Lupus)

54
Q

Outline type 4 hypersensitivity?

A

Slowest - T-cell mediated
Dendritic cells with antigens migrate to lymph nodes > Present to T cells
T cell clones proliferate and migrate to site of inflammation
TNF secreted by Macrophages and T cells and stimulate damage

55
Q

RA is what type of hypersensitivity?

A

Type 4

Th1, Th17 and TNF mediated

56
Q

What antigens drive RA?

A

Citrullinated proteins (arginine > citrulline

57
Q

Outline the pathophysiology of RA?

A

Citrullinated proteins act as antigens which are recognised by T and B cells, these produce antibodies
(Anti-cyclic citrullinated peptide antibodies)
Synovium infiltrated by T(h1,17) cells, macrophages
TNF and IL-17 activate neutrophils and osteoclasts, creating erosions

58
Q

What are the risk factors for RA?

A

Smoking
HLA-DR4
Porphyromonas infections

59
Q

Outline the pathophysiology of MS?

A

Th1, 17 cells and macrophages develop inflammatory lesions of the CNS
Myelin loss causes neurological symptoms
Recovery between attacks
Chronic disability due to AXONAL loss

60
Q

Name 3 T-cell mediated delayed hypersensitivity (type 4) conditions?

A 
RA
MS
T1DM
IBD
Psoriasis
Coeliac
61
Q

How is delayed hypersensitivity treated?

A 
Anti-inflammatory drugs
NSAIDS, Corticosteroids
Anti-TNF
Anti-IL-6
B-cell antibodies
Immunosuppressants
62
Q

Name 3 type 3 hypersensitivity conditions?

A

Farmer’s lung
Post-streptococcal glomerulonephritis
Lupus

63
Q

Name 3 type 2 hypersensitivity conditions?

A

Graves’ Disease
Blood transfusion reactions
Haemolytic disease of the newborn
Drug-induced haemolysis

*Haematology + Immunology (22 decks)

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