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A-Level Flashcards on various topics > Immuno- Primary immune deficiencies > Flashcards

Immuno- Primary immune deficiencies Flashcards

1
Q

How are T cells selected in the thymus?

A

Depends on their affinity for HLA

  • low affinity = not selected
  • high affinity = negative selection due to auto reactivity
  • intermediate affinity = positive selection
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2
Q

How do lymphoid progenitors become CD4 or CD8?

A

Lymphoid progenitors express both CD4 and 8. If they bind with intermediate affinity to MHCII –> become CD4
Bind with intermediate affinity to MHCI –> become CD8

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3
Q

2 ways in which CD8 cells kill cells directly?

A

Perforin + granzymes

Expression of Fas

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4
Q

CD4+CD25+Foxp3+ ?

A

Treg cells

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5
Q

Th17 cells - what do they do?

A

Aid neutrophil recruitment

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6
Q

Describe DiGeorge syndrome

  • Mnemonic for clinical features?
  • B and T cell levels?
  • Does immunity change with age?
A

2q11.2 deletion syndrome
CATCH - 22
Cardiac defects, Abnormal face (high forehead, low set ears), Thymic aplasia, Cleft palate, Hypocalcemia/hypoPTH, 22q11.2 deletion

B cells normal. T cells low (due to thymic aplasia)

Homeostatic proliferation with age –> immune function improves!

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7
Q

V low CD4 count
Normal CD8 cell count
Low IgG, low IgA

A

Bare lymphocyte syndrome Type 2

  • due to absent expression of MHC class II –> no CD4 cells develop from lymphoid progenitors!
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8
Q

4 Hx features of bare lymphocyte syndrome

A
  1. Failure to thrive at 3 months
  2. Infections
  3. Prone to sclerosing cholangitis
  4. FHx of infant death
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9
Q

2 types of disorders of T-cell effector function + egs.

A

Cytokine/receptor deficiency (IL12 and IFNgamma)

Failure to communicate with B cells = HyperIgM syndrome (where T cells fail to express CD40L)

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10
Q

Most common form of SCID? cause? how does it cause any problems?

A

X-linked SCID
Mutation of gamma chain of IL2-RECEPTOR

–> inability to respond to cytokines involved in lymphoid development

  • -> arrest of T +NK cell development
  • -> increased immature B-cells
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11
Q

Phenotype of SCID?

Levels in X-linked SCID
T cells? B-cells? Thymus?

A

Unwell at 3 months + failure to thrive, persistent diarrhoea, bare infections

  • Vv low T-cells
  • Normal/raised B cells
  • Poorly developed thymus
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12
Q

T-cell deficiencies increases your risk of…?

A

INTRACELLULAR pathogens
- TB, salmonella

Viral - CMV
Fungal - PCP

early MALIGNANCYA

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13
Q

Ix for suspected lymphocyte deficiencies?

A 
WCC
Lymphocyte subsets
serum Ig
Functional tests
HIV
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14
Q

5 avenues of Mx for T-cell deficiencies

A
  1. Aggressive prophylaxis/Tx of infection
  2. SC transplantation
  3. Ig replacement
  4. Enzyme replacement for ADA SCID
  5. Experimental - thymus transplant in DiGeorge, gene therapy
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15
Q

How do B-cells produce different classes of Ig?

A

Immature B-cells produce IgM.

Once activated by signalling via cytokine receptors by T-helper cells, they switch to producing IgA/E/G

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16
Q

Which type of T-cell deficiency will affect antibodies?

A

CD4 T-helper cells

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17
Q

Most severe B-cell deficiency? Aetiology? Ix results? Presentation?

A 
Bruton's X-linked hypogammaglobulinaemia
Due to BTK gene defect
Arrest of B-cell maturation 
- Low B-cells and all Igs
- recurrent infections in childhood (bacterial, enterovirus)
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18
Q

B-cell deficiency where class switch is affected?
Aetiology?
Presentation - any specific pathogens?

A 
HyperIgM syndrome
CD40L gene (Chr Xq26) is mutated on T-helper cells --> B-cells aren't activated to class switch

Boys - present in 1st few years of life: recurrent bacterial infections
esp PCP
Also autoimmunity + malignancy - esp NHL

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19
Q

Ix results in HyperIgM syndrome

A

High IgM. Low IgA/E/G

Normal B and T cells.

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20
Q

Heterogenous group of disorders where disease mechanism is unknown
Low IgG, IgA and IgG

A

Common variable immune deficiency

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21
Q

3 main clinical features of common variable immune deficiency w egs

A
  1. V severe recurrent bacterial infections (w end organ damage)
    - bronchiectasis, sinusitis, GI infection
  2. Autoimmune disease
  3. Granulomatous disease
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22
Q

Results on electrophoresis in Bruton’s

A

No signal for Gamma

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23
Q

Antibody/B-cell deficiencies: susceptible to what kind of infections

A

Bacterial!!!!
Toxins - tetanus, diphtheria
Entroviruses

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24
Q

What measurement is a surrogate marker for CD4 T-helper cell function

A

IgG

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25
Q

Mx of B-cell deficiencies?

A

Aggressive Tx of infection
Ig replacement every 3 weeks
BM transplant

26
Q

Specific management of IgA deficiency

A

Immunisation

27
Q

Adult with bronchiectasis, recurrent sinusitis and development of atypical SLE - which B-cell deficiency?

A

Common variable immunodeficiency (the combo of immunodeficiency + autoimmunity)

28
Q

Recurrent bacterial infection in a child, episode of PCP, high IgM, absent IgA and IgG…which B-cell deficiency?

A

X-linked hyper IgM

29
Q

1 year old boy with recurrent bacterial infections

CD4 and CD8 T cells normal. B cells absent. IgG, IgA and IgM absent

A

Bruton’s X-linked hypogammaglobulinaemia

BTK gene mutation –> inability for B cells to mature

30
Q

Recurrent respiratory tract infections, absent IgA, normal IgM and IgG

A

IgA deficiency

31
Q

Severe recurrent infections from 3 months old.
CD4 and CD8 T cells and NK cells absent.
B cells present. Igs normal.
Normal facial features and cardiac echo.

Which lymphocyte deficiency is this?

A

X-linked SCID

Gamma chain of IL2 receptor is defected. Inability to respond to cytokines –> early arrest of T cell and NK cell development

32
Q

Young adult with chronic infection with mycobacterium marinum.
Which lymphocyte deficiency is this?

A

IFNgamma or IL12 deficiency or defect of their receptors

33
Q

Recurrent infections in childhood, abnormal facial features, congenital heart disease, normal B cells, low T cells, low IgA and IgG
- which lymphocyte deficiency is this?

A

DiGeorge syndrome

Thymic aplasia --> low T cells. 
Low T cells --> inability for B-cells to class switch --> low IgA and IgG
34
Q

6 month baby with 2 recent serious bacterial infections, T cells present but only CD8+.
B cells present. IgM present but IgG low.
Which lymphocyte deficiency is this?

A

Bare lymphocyte syndrome type II

Deficiency of functional MHC class II, therefore no development of CD4 T cells.

35
Q

Recurrent infections with high neutrophil count on FBC but no abscess formation
Which phagocyte deficiency is this?

A

Leukocyte adhesion deficiency

36
Q

Recurrent infections with hepatosplenomegaly and abnormal dihydrorhodamine test

Which phagocyte deficiency is this?

A

Chronic granulomatous disease

Deficient in a component of NADPH oxidase –> inability to kill via oxidative killing.

37
Q

Recurrent infections with no neutrophils on FBC

Which phagocyte deficiency is this?

A

Kostmann syndrome

38
Q

Infection with atypical mycobacterium. Normal FBC.

What phagocyte deficiency is this?

A

IFN gamma receptor deficiency

39
Q

Meningococcal meningitis with FHx of sibling dying of same condition aged 6.
Which complement deficiency is this:
C7? C3? MBL? C1q?

A

C7 - terminal common pathway defect –> inability to lyse encapsulated bacteria

40
Q

Membranoproliferative nephritis and bacterial infections

Which complement deficiency is this?
C7? C3 with presence of a nephritic factor? MBL? C1q?

A

C3 deficiency with presence of a nephritic factor (an autoantibody against parts of complement pathway which stabilises C3 convertases)

41
Q

Severe childhood onset SLE with normal levels of C3 and C4.

Which complement deficiency is this?
C7? C3 with presence of a nephritic factor? MBL? C1q?

A

C1q: deficiency of early classical pathway.

Immune complexes fail to activate the complement pathway + increased load of self-antigens esp against nuclear components.

42
Q

Recurrent infections when receiving chemotherapy but previously well.

Which complement deficiency is this?
C7? C3 with presence of a nephritic factor? MBL? C1q?

A

MBL deficiency

  • this deficiency is rarely problematic unless there is a coexisting cause for immune impairment
43
Q

Most severe primary immune deficiency ?
Cause?
Management?

A

Reticular dysgenesis

  • AK2 mutation –> failure of cells to differentiate along Myeloid + Lymphoid lineage
  • Mx: fatal without urgent BM transplantation
44
Q

Episodic neutropenia every 4-6 weeks with periods of good health?

What is this condition? What is the cause?

A

Cyclic neutropenia

Mutation in ELA-2 (neutrophil elastase)

45
Q

What is deficient in Leukocyte adhesion deficiency?

A

CD18 deficiency - this usually is expressed by neutrophils and binds to endothelial cells for adhesion + transmigration

46
Q

3 features of leukocyte adhesion deficiency

A
  1. Normal neutrophil count on FBC
  2. Absence of pus and abscess
  3. Delayed umbilical cord separation
47
Q

Name of disease where oxidative killing mechanism is impaired? How does this happen?

A

Chronic granulomatous disease

Deficiency of a component in NADPH oxidase

48
Q

Which bacterial infections are patients with CGD prone to?

A

PLACESS

Pseudomonas, listeria, aspergillus, Candida, E Coli, staph aureus, serratia

49
Q

2 Ix which are abnormal in CGD?

A

NBT and DHR

50
Q

Which primary immune deficiency is associated with mycobacterial infection?

In this deficiency, what are its unable to form?

A

IFNgamma/IL12 or their receptor deficiency

These are required for activation of oxidative killing

Inability to form GRANULOMAS

51
Q

Ix for suspected phagocyte deficiencies?

A

FBC
Leukocyte adhesion markers
NBT or DHR (for oxidative killing in CGD)
Pus/abscess formation

52
Q

In NK deficiency, what is a patient susceptible to? Mx?

A

VIRAL infections: HSV, VZV, EBV, CMV, HPV

prophylactic antivirals

53
Q

2 types of NK cell deficiency? What are their causes?

A

Classical = the absence of NK cells.
- GATA2 + MCM4

Functional = abnormal function
- FCGR3A

54
Q

The classical complement pathway - what is it activated by?

Classical pathway deficiency is associated with….?

A

Activated by immune complexes

  • associated with SLE = due to increased load of self-antigens
55
Q

Secondary deficiency of the classical complement pathway - what is it?!

A

Active SLE –> persistent production and consumption of complement

56
Q

Which complement deficiency is quite common? when is it a problem?

A

MBL deficiency - only problematic with co-existing cause of immunodeficiency eg chemotherapy

57
Q

2 things which patients with C3 deficiency are susceptible to?

A
  1. Infection with encapsulated bacteria (meningococcus, strep, haemophilia)
  2. connective tissue disesase
58
Q

WTF is secondary C3 deficiency

Assoc with?

A

Nephritic factors present : they are directed against parts of the complement pathway.

They STABILISE C3 CONVERTASES –> increased C3 consumption

Associated with glomerulonephritis

59
Q

4 Ix used to determine complement deficiencies?

A

C3, C4, CH50, AP50

60
Q

SLE is associated with deficiencies in which components of the complement pathway?

A

C1,2, and 4

A-Level Flashcards on various topics (69 decks)

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