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Paediatrics Study > Immunology > Flashcards

Immunology Flashcards

1
Q

Is neutrophil half life in the blood short or long?

A

Short, 7 hours

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2
Q

Liver abscess is commonly associated with which primary immunodeficiency disorder?

A

Chronic granulomatous disease

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3
Q

What is Kostmann syndrome?

A

Congenital neutropenia, promyelocytes can’t mature. HAX1 gene mutation. Aut rec

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4
Q

Which disorder has poor neutrophil + macrophage function due to deficient NADPH oxidase?

A

Chronic granulomatous disease

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5
Q

NADPH oxidase deficiency leads to inability to convert oxygen to superoxide. What is the next step in the ‘respiratory burst’?

A

Production of hydrogen peroxide from superoxide, using superoxide dismutase

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6
Q

Which organisms contain the enzyme to break-down hydrogen peroxide, hence rendering them protected in CGD?

A

Catalase positive organisms (Staph aureus, Aspergillus) - body can’t kill them, so surrounds them and forms granulomas

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7
Q

Gold standard test for CGD diagnosis?

A

Dihydrorhodamine 123 - turns fluorescent green

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8
Q

In CGD, are T+B cells normal?

A

Yes

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9
Q

In CGD, are Ig normal, high or low?

A

Often high due to chronic inflammation/infections

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10
Q

Which prophylaxis is recommended for neutrophil disorders?

A

Bactrim (broad gram negative + Staph prophylaxis)

Itraconazole (good Aspergillus prophylaxis)

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11
Q

3 cardinal features of Leucocyte Adhesion Deficiency?

A

Acronym LAD:
Late separation umbi
Absent pus/nil abscesses/poor wound healing
Dysfunctional neutrophils - can’t move to where they are required (absent CD18 on leucocytes which is required for adhesion/integrin; and high neutrophils in blood as can’t move to tissues)

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12
Q

Explain the Complement classical pathway

A
  • C1 -> antibody-antigen complex or CRP -> C4 -> C2

C4 -> C3 -> common pathway (MAC: C5-9)

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13
Q

Explain the Complement lectin pathway

A
  • C4 mannose-binding lectin (ie binding of this protein to pathogen carbohydrate) -> 2
  • C4 -> 3 -> common pathway
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14
Q

Explain the Complement alternative pathway

A
  • constant low-grade activity (ie ready to escalate if needed)
  • C3 from classical pathway or from touching microbial surface can cleave -> C3b -> C5-9
    C3b -> C3 can re-stimulate to amplify response
    Protein B/D and Properdin required for alternative pathway
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15
Q

Deficient C1 esterase inhibitor can lead to what condition?

A

Hereditary angioedema

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16
Q

What is the management of hereditary angioedema?

A

Danazol (androgen) which increases C1 esterase inhibitor levels

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17
Q

Recurrent Neisseria is associated with which part of the Complement system?

A
  • MAC: C5-9

- Properdin deficiency

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18
Q

Which virus is most associated with agammaglobulinaemia?

A

Enterovirus

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19
Q

What is the common cause of diarrhoea in antibody disorders?

A

Giardia

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20
Q

What are the key organisms associated with antibody disorders?

A 
Encapsulated: Strep pneumo, HiB
Staph aureus, Pseudomonas 
Enterovirus
Giardia
Polio risk from live vaccine
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21
Q

Is lymphoid tissue ie tonsils present in agammaglobulinaemia?

A

No

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22
Q

At what stage are B cells arrested in x-linked agammaglobulinaemia?

A

Pre-B -> thus unable to form antibodies as aren’t mature plasma cells

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23
Q

What is the enzyme implicated in x-linked agammaglobulinaemia?

A

Btk (tyrosine kinase) on Xq22

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24
Q

CVID is due to partial impairment of T cell development and function leading to risk of infection + autoimmunity. Is lymphoid tissue ie tonsils present?

A 
Yes: normal or enlarged
Commonly associated with splenomegaly 
- B cells: N or low
- T cells: variable number 
- Low Ig
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25
Q

CVID is associated with increased occurrance of which cancer?

A

EBV associated lymphoma

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26
Q

IgA is found in which parts of the body? Is IgA higher in tissues or blood?

A

Mucosa: resp, GIT

Higher in tissues (MALT), low in blood

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27
Q

What 2 main signals stimulate B cells to produce IgA?

A

Il-5

TGF-beta

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28
Q

In IgA deficiency, which Ig is commonly elevated as B cells try to compensate for reduced IgA?

A

IgE = allergy risk

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29
Q

How common is IgA deficiency?

A

1/500

Most common PID

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30
Q

Which PID is associated with risk of severe reactions to blood products?

A

IgA deficiency

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31
Q

Poor response to polysaccharide vaccines is the best marker for which antibody condition?

A

IgG subclass deficiency

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32
Q

In the bone marrow, which Ig do B cells have on their surface?

A

IgD and IgM

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33
Q

How many receptors does each B cell have, which are capable of binding to the same antigen?

A

100,000

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34
Q

Which ligand do CD4 T cells express when they bind to B-cell+MCHclass2/antigen complex?

A

CD40 ligand - which attached to CD40 receptor on B cell

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35
Q

Class switching changes what part of the Ig?

A

Heavy chain determines Ig class

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36
Q

Ectodermal dysplasia (abnormal teeth, skin, nails, hair, reduced sweating) is associated with which primary immunodeficiency?

A

Hyper IgM syndrome

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37
Q

What is the inheritance of hyper IgE syndrome?

A

Autosomal dominant, STAT3 defect

38
Q

Hyper IgE syndrome has elevated IgE with normal IgA, IgG and IgM. Which cell is commonly elevated in hyper IgE syndrome?

A

Eosinophils

39
Q

Hyper IgE syndrome is associated with which 3 key features?

A

Staph: abscess/pneumatocoele
Rash, ‘eczema’
Reduced vaccine/cell mediated response

40
Q

Fractures and failure to shed primary teeth is associated with which immunodeficiency?

A

Hyper IgE syndrome

41
Q

Which class of PID are associated with fatal reaction with live vaccines and high risk of maternal engraftment of T cells?

A

T cell defects / SCID

42
Q

How is SCID detected on NST?

A

Reduced T cell receptor excision circles (maker of thymopoiesis)

43
Q

25% of SCID is x-linked. Mutation for IL2RG gene that codes for common gamma chain receptor is found on which chromosome?

A

Xq13.1

44
Q

Common gamma chain receptor in SCID affects which interleukin receptors?

A

IL2, 4, 7, 9, 15, 21

45
Q

Which Igs trigger Classical pathway?

Which Ig triggers Alternative pathway?

A
  1. IgM & IgG

2. IgG

46
Q

Which immune cells produce the most cytokines?

A

CD4 helper T cells

47
Q

Th1 cells are important for which pathogens?

A

Intracellular

48
Q

Th2 cells are important for which pathogens + which other conditions?

A

Extracellular

Atopy

49
Q

Which cytokines promote Th1 + Th2 cell production?

A

Il-12 -> Th1

Il-4 -> Th2

50
Q

Th1 cells produce which cytokine? & what does it do?

A

Interferon gamma

Important for B cells to make IgG for opsonisation and activates macrophages

51
Q

Th2 cells produce which cytokines? & what do they do?

A

Il-4, 5, 13 = important for IgE + eosinophils

Il-10 = antiinflammatory

52
Q

What is class switch recombination?

A

Antibody process of changing mu heavy change to change Ig class

53
Q

What is the most common cause of hyper IgM syndrome?

A

X linked inherited defect of CD40 ligand gene (TNFSF5 gene) - this is expressed on activated CD4+ T cells and is required to interact with CD40 on B cells to enable class-switch recombination
= combined immunodeficiency
–> from infancy
–> sinopulmonary infections, esp encapsulated
–> opportunistic infections, PJP occurs in 40% and may be first feature
–> diarrhoea/cryptosporidium common
–> higher risk for malignancy/autoimmune/cytopenia

Normal number of B cells, but reduced CD27+ (memory) and no IgD+CD27+ (switched memory) cells
Normal/high IgM
Low IgG/IgA/IgE
Poor response to protein + polysaccharide vaccines
2/3rds neutropenic

Second most common cause: AID and UNG enzyme deficiencies, involved in class-switch recombination
= humeral immunodeficiency
–> recurrent sinopulmonary infections -> bronchiectasis risk
–> & lymphoid hyperplasia
Commonly presents age 2

54
Q

Neutrophil disorders - number or function. Number issues?

A
  1. Severe congenital neutropenia / Kostmann syndrome (HAX1 mutation)
  2. Cyclical neutropenia (ELANE mutation) : normal between drops
  3. X-linked neutropenia (Wiskott-Aldrich Gene mutation) : persistent
55
Q

2 year old boy
Term
PHx staph aureus cervical lymphadenitis at 7 months of age
Presented with skin abscess: + for Serratia Marcessens (unusual pathogen)
Brother and father have recurrent abscesses

A

Chronic granulomatous disease

1:250,000
Defect in NADPH oxidase enzyme complex
Needed for neutrophils to make ROS - needed for pathogen killing 
Most X-linked, gp91phox mutations 
Infections: bacterial, fungal
- Catalase positive organisms; Staph aureus, Aspergillus (bilat pneumonia), Nocardia, Burkholderia
- adenitis 
- abscess esp LIVER abscesses
Inflammatory (IBD) / Granulomas

Mx: bactrim, itraconazole; aggressively mx infections; HSCT

56
Q

9 year old girl
Recurrent otitis media from age 2
Recurrent staph skin infections, multiple courses of antibiotics
Presents now with pneumonia

A

Autosomal recessive CGD

- some residual NADPH oxidase function: better prognosis

57
Q

11 month old male
Hx delayed umbilical cord separation (up to 3 weeks can be normal)
Large ulcerated skin lesion in nappy area, minimal pus at site of ulcer, WCC 48

A 
Leucocyte adhesion deficiency
Aut recessive
Peripheral leucocytosis + neutrophilia
Recurrent bacterial infections
Absent pus, poor wound healing
Delayed cord separation, omphalitis 
Gingivitis

LAD1

  • most common
  • beta2 integrin gene mutation (CD18)

LAD2
- CD15 mutation

LAD3

  • mutation in KINDLIN3 required for beta1, 2 and 3 integrins
  • bleeding tendancy

Mx: aggressively treatment infections; HSCT for LAD1 and 3; IL23 & IL12 blocker ustekinumab

58
Q

Poor wound healing

Periodontitis

A

Disorders of chemotaxis

59
Q

Clues to neutrophil disorder

A

Neutropenia or neutrophilia

Aspergillus or Burkolderia

60
Q

What are toll like receptors?

A

Part of innate immune system
Expressed by antigen presenting cells
Type 1 transmembrane receptors
Recognise molecular structures of bacteria/viruses/fungi/parasites
&
Intracellularly cause signals ie MyD88 & IRAK4
to up-regulate immune response to that pathogen

Important in early life when adaptive immunity not so good yet

61
Q

IRAK4 / MyD88 deficiency

A

Toll like receptors unable to initiate innate immune response as these are important signalling molecules downstream from toll like receptors

Aut recessive
Recurrent bacterial infections - strep pneumo, staph aureus
Poor inflammatory response: minimal fever, minimal CRP rise
Young children

Ix: CD62L shedding
Mx: immunisation, prophylactic antibiotics

62
Q

Anhidrotic ectodermal dysplasia

A

Defect in:
NEMO (x linked) gene – end pathway of toll like receptors
or
IKBA (aut dominant) gain of function

Viral & bacterial (pneumococcus) & fungal (candida) & atypical mycobacteria

Sparse hair, sparse conical teeth (pointy), can’t sweat

63
Q

Candida immune response

A

Dectin-1, CLR receptors

  • > Th17 cell (STAT 3) -> Th1 helps (STAT 1)
  • -> IL23, IL17
64
Q

Recurrent/persistent candida (skin, mucous membranes, nails)
+
Endocrinopathy / Autoimmune / Immunodeficiency

A

Chronic mucocutaneous candidiasis

– CARD9 deficiency = candida meningitis

65
Q

STAT 1 role?

A

Important intracellular protein
Important for VIRAL immune response
Up-regulate interferon-gamma responses

STAT 1 loss of function = overwhelming viral infection

Partial loss of STAT 1 = mycobacterial infection risk

Ix: STAT 1 phosphorylation

STAT 2 loss of function = severe viral infection, MMR vaccine related measles infection

66
Q

Susceptibility to human papilloma virus?

A 
WHIM: 
warts
hypogammaglobulinaemia
immunodeficiency
myelokathexis/neutropenia (can't move neutrophils from bone marrow due to lack of chemokine receptor: CXCL4)

EXER:
warts only

67
Q

Susceptibility to mycobacterial disease?

A

IL12, IL18, IL23
Interferon gamma
STAT 1 partial loss of function

68
Q

2 clues to innate immune defects:

A

Lack of fever/CRP response

Severe/recurrent disease with INDIVIDUAL pathogen eg HSV/HPV/candida

69
Q 
Major part of innate immunity
60 plasma and membrane/cell surface proteins 
3 activating pathways
End in common lytic terminal cascade
Potant regulators
A

Complement system

70
Q

3 roles of complement:

A
  1. Opsonisation
    & aid phagocytosis:
    C3b or C4b binds to microbe
  2. Recruit + activate leucocytes: by C3a, C5a
  3. Osmotic lysis of microbe by membrane attack complex: C3b bound to microbe activates MAC
71
Q

3 ways to activate pathway

A
  1. Classical: Ag-Ab
    C1q (REGULATOR: C1 esterase inhibitor), C4, C2
  2. Lectin: lectin binding to mannose
    C4, C2
  3. Alternative: pathogen or apoptosis
    C3b, factor B, factor D, p (factor H and I are REGULATORS)

–> C3 (C3 convertase) -> C3a (inflammation), C3b (opsonisation)
(REGULATORS: CR1, CD46, DAF)

–> C5 (C5 convertase) -> C5a (inflammation), C5b (initiates MAC)
(REGULATOR: CD59)

–> MAC: C5b, C6, C7, C8, C9

72
Q

Low C4?

A

Consider Classical pathway problem

73
Q

Low C3, normal C4?

A

Consider Alternative pathway problem

74
Q

Deficient in C1, C2 or C4 (classical pathway) predisposes to?

A

Autoimmune disease

Especially SLE - development of autoantibodies to nuclear proteins

75
Q

Deficiency of C1 esterase inhibitor leads to?

A

Hereditary angioedema
– autosomal dominant

Classical pathway uncontrollably activated –> Increased activation of Factor X11 and bradykinins = increased vascular permeability + angioedema

    • cutaneous
    • airway
    • GIT: abdo pain + vomiting

NO URTICARIA as it is not mast cell driven (the swelling is NOT itchy in hereditary angioedema)
- may have rash called erythema marginatum

Ix: C1 inhibitor defect = reduced C1 esterase inhibitor function assay & level (may have normal level but poor function!)

Attacks can be triggered by illness, trauma or spontaneous

Mx of attacks: Tranexamic acid, Danazol, C1 esterase inhibitor replacement

76
Q

Deficiency of Alternative pathway / propordin / factor B: predisposes to?

A

Encapsulated organism infection esp Strep and Neisseria

77
Q

Factor H and I deficiency leads to:

A

Uncontrolled activation of Alternative pathway –> Atypical haemolytic uraemic syndrome

78
Q

Normal CH50, low AP50

A

Alternative pathway defect

79
Q

Low CH50, normal AP50

A

Pre-C3 classical pathway defect

80
Q

Low CH50 + AP50

A

MAC defect
= recurrent meningococcal, disseminated gonococcal infections

OR

C3 deficiency = abscess, OM, pneumoniae, bacteraemia

81
Q

Normal CH50 + AP50

A

Properdin defect = recurrent meningococcal infection

82
Q

Clues to complement defect:

A

Recurrent meningococcal / Hib / pneumococcal

Angioedema without urticaria/itch

83
Q

Intrinsic T cell defect, CD40 ligand issue
Normal number of B cells
Low Igs
Presents:
- Early in life
- Opportunistic infections esp PCP pneumonia and cryptosporidium diarrhoea

A

Hyper IgM

84
Q

Difficulty progressing from B cell to plasma cell
Low IgG, low IgA
Normal or low IgM
Nil B memory cells; poor antibody response
No T cell problem
Diagnose after age 4
High risk of autoimmunity / cytopenias

A

CVID

85
Q

Medications which can cause hypogammaglobulinaemia

A

Steroid
Captopril
Carbamazepine, phenytoin
Anti-malarials

86
Q

Vaccine requiring: T dependent antibody response (ie protein)
IgG, IgA, IgE

A

Tetanus

Diptheria

87
Q

Vaccine requiring: T independent antibody response (ie polysaccharide)
IgM, shorter lived

A

Pneumovax 23 (conjugate)

88
Q

Minimal fever
Minimal CRP
Age 1, pneumococcal meningitis
Consanguineous parents

A 
Toll-like receptor defect
Autosomal recessive: 
IRAK4
Myd88 
Impaired proinflam cytokine production: IL1, IL6 (responsible for CRP: from Hep3B cells)
IL1, IL6, TNF important for fever
89
Q

Ectodermal dysplasia

A

NEMO

90
Q

Absence of normal downregulation of macrophages, NK cells, CD8 cells -> cytokine storm: secrete ++ cytokines (IL2 = CD25, 6, 10, 12) & interferon gamma, TNF alpha, & phagocytose host cells (red cells / platelets / white cells). NK/CD8 cells unable to get rid of the excess activated macrophages.
Can be triggered by infection (most commonly EBV) or sporadic
MAS is a form of this condition, which is associated with juvenile idiopathic arthritis

Fever, organ involvement ie hepatitis/abnormal coags, neuro involvement, splenomegaly
Ix: CYTOPENIA, high trigs, high ferritin (macrophages are a primary source of ferritin), low fibrinogen, high CD25 (alpha chain of IL2 soluble) - related to disease activity, low NK activity (flow cytometry for surface expression of CD107alpha, also called LAMP-1 [lysosomal-associated membrane protein 1])

A

HLH

91
Q

2 weeks post strep pharyngitis
Carditis, arthritis
Less commonly: migrating rash, subcut nodules, chorea
Presumed pathogenesis?

A

Molecular mimicry with bacterial antigen

- mimics with myosin

Paediatrics Study (11 decks)

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