PATH30001 - Mechanisms of Disease > Lecture 11 - Immunodeficiencies > Flashcards

Lecture 11 - Immunodeficiencies Flashcards

(42 cards)

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1
Q

What is innate immunity made up of?

A

First line:
• Physical barriers
• pH
• Secretions

Second line:
• Innate immune cells

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2
Q

Describe the role of DC’s

A
  • ‘Sentinels’
  • Link between innate and adaptive immunity
  • PAMP recognition with PRRs
  • T-lymphocyte co-stimulation
  • Nature of their function dependent on cytokine signalling
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3
Q

What are the critical features of adaptive immunity?

A
  • Slower to be induced
  • Memory function
  • Recognises specific antigen
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4
Q

What are the different type of B cells?

A
  • B-1
  • B-2
  • Marginal zone B cells (MZB)
  • Follicular B cells
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5
Q

Describe the kinetics of immune protection after vaccination

A

→ Vaccination

  1. Induction of the primary immune response; IgM
  2. Response dies back, pool of memory cells present

→ Exposure to antigen from environment
3. Induction of immune response more quickly and to a greater magnitude; IgG, IgA

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6
Q

What are the main difference between the primary and secondary immune responses?

A

Secondary:
• greater magnitude
• more quickly induced
• class switched Ig (e.g. IgG, IgA)

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7
Q

Can IgA or IgM be monomers?

A

IgM: no
IgA: yes

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8
Q

What is the structure and function of memory B cells?

A
  • Surface bound immunoglobulins

* hang around after the immune response has been resolved, waiting for the next exposure to the antigen

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9
Q

Compare T-dep. and T-independent antigen, and the respective immune responses

A

T-dependent:
• usually protein
• T cell help available to B cells
→ longer lived, more robust response

T-independent: 
 • polysaccharide
 • no T cell help available to B cells 
→ short lived response
 • no SHM or CSR
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10
Q

Describe the role and function of Treg

A 
Suppressive effects on:
 •  granulocytes
 • DC's
 • B cells
 • Th2
 • Th1
 • Th17
 • T cell migration to tissues
Under normal conditions, control allergy, autoimmunity and inflammation
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11
Q

What are the markers of Treg?

Why is this important?

A
  • CD25
  • CD4

• FoxP3 (transcription factor)

Deficiency in FoxP3 leads to deficiency of Treg.
This is called IPEX syndrome

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12
Q

What are the generalised outcomes of immune system defects?

A
  • Autoimmunity
  • Allergy
  • Immunodeficiency
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13
Q

Define Immunodeficiency

A

A group of disorders where part of the immune system is missing or defective

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14
Q

What are the two categories of immunodeficiency?

Give examples for each

A

Primary: inherited (HIGM)
Secondary: acquired (HIV/AIDS)

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15
Q

What is PID?
Describe some features.
When is the onset?
What are the various classes?

A

Primary immune deficiency
• 150 different conditions
• most are rare
• inherited

Onset is usually in childhood, but can in adulthood

Classes in order of prevalence:
 • Antibody
 • Combined
 • Phagocytic
 • Cellular
 • Complement
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16
Q

What are clinical signs of PID used for diagnosis?

A

Combination of patient history w/ lab tests

Patient history:
 • >10 cases of otitis media per year
 • >2 cases of pneumonia
 • >2 life threatening infections per lifetime
 • >2 sinus infections per year

Lab tests:
• Low Ig levels (in general, or of specific classes)
• Cellular deficiencies

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17
Q

What are the pathological features of PID?

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A

• Recurrent deep skin or organ abscesses

• >2 deep-seated infections such as meningitis,
osteomyelitis, cellulitis or sepsis

  • oral thrush or Candida infection
  • Autoimmune phenomena
  • Dysmorphic features associated with recurrent infection
  • Infections that worsen chronic disorders (eg. asthma)
  • Infections with pathogen despite vaccine (eg pneumococcal)
18
Q

Give some specific examples of PID

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A
  1. T cell
    • IPEX
    • SCID
  2. B cells
    • CVID
    • SAD
  3. Innate deficiency
    • Chronic granulomatous disease
    • IRAK-4
19
Q

What are some Antibody deficiencies?

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A
  • CVID
  • SAD

(HIGM, agammaglobulinaemia; but these aren’t death with in this lecture)

20
Q

What are some T-cell deficiencies?

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A
  • SCID (severe combined immune deficiency)

* IPEX syndrome

21
Q

Describe the general features CVID

What is the cause?

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A

Normal numbers of B cells, but they do not develop properly in plasma cells to produce Ab

  • One of the most common PID’s
  • V. low levels of serum Ig
  • Increased susceptibility to infection due to this Ab deficiency

• Affects multiple organs (lungs, GIT, spleen, ears, blood)

Causes:
Mutations in:
• TACI
• ICOS
• CD19
22
Q

What are the pathological outcomes of CVID seen around the body?

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A 
1. Frequent lung infections
• Sinusitis
• Pneumonia
• Bronchitis
• Otisis
  1. Enlarged lymph nodes & spleen
  2. Polyarthritis
23
Q

What are the treatment options for CVID?

What about SAD?

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A
  • Intragam (IVIg)
  • Antibiotics for the infections

Same for SAD

24
Q

What is the main features of SAD?
What is lacking?
What isn’t?

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A

(Specific antibody deficiency)
• Failure to produce normal Ab levels against specific polysaccharide antigens
(IgG2?)

NB
• Normal general Ig levels, and normal Ig subclasses, and normal response to protein antigens
• It is only Ig against very specific antigens that are absent

25
What is the main complication of SAD? | Why?
Pneumococcal infection Antigen that is normally recognised by the immune system is polysaccharide In SAD, there is failure to produce antibody against polysaccharide antigens
26
Which people are most commonly affected by Pneumococcal disease and why?
Who: Children, elderly, SAD patients Reason: • The antigen is T-cell independent • Children are yet to develop the required response • Immunocompromised individuals lack the response • Elderly has lost the required response
27
What is an important structural feature of S. pneumoniae?
Polysaccharide capsule
28
Describe how SAD is diagnosed in the lab
1. Response to pneumococcal polysaccharide antigens • Patient exposed to 23 different p.p. antigens • If the patient responds to less than half, we diagnose with SAD (NB respond indicates IgG specific for the antigen produced) 2. No memory B cells • Using flow cytometry
29
What's wrong with 'Bubble boy'?
SCID: severe combined immune deficiency
30
Describe the features of SCID, as well as the cause(s)
Immune system lacks: • T cells • B cells • NK cells • Severe susceptibility to infection ``` Cause: • Many genetic causes identified to date e.g.; • cγ mutation • IL-7α • JAK3 ```
31
What is IPEX syndrome? | Describe some features including pathogenesis
(Immunodysregulation polyendocrinopathy enteropathy X- linked syndrome) • Very rare Pathogenesis: • Mutation in FoxP3 (marker of Tregs) • Lack of functional Treg → multiple autoimmune disorders and allergies
32
Describe the pathology of IPEX
* Absence of small bowel mucosa * Inflammatory infiltrate in many organs * Steatosis in liver * Nephritis * Eczematous skin * No goblet cells * Atrophy of villi in duodenum
33
What is Chronic granulomatous disease? | What is the cause?
* Innate immune deficiency * Neutrophils / macrophages cannot produce superoxide * Cannot kill phagocytosed bacteria Cause: • Mutations in NAPDH oxidase
34
What are some examples of innate immune deficiency?
* IRAK-4 deficiency | * Chronic granulomatous disease
35
What is IRAK-4?
Interleukin-1 receptor associated kinase-4 It is a protein kinase involved in the intracellular transduction pathway after TLRs and Interleukin signalling
36
Describe the pathogenesis of IRAK-4 deficiency | Which infections will one be susceptible to?
* Lack of IRAK-4 * Impaired IL-1 and TLR signalling * Impaired T-cell activation Infection: • Susceptible to pyogenic bacteria • Not susceptible to viruses or fungi
37
Which disorders can probiotics help?
Some success seen in allergies
38
Which 'helper' T cell is usually induced in an immune response?
Th1
39
What is the function of Th2?
Helminth immunity | Allergy
40
What is the function of Th17?
Immunity against extracellular bacteria
41
Which classes of Ig can be transported across the mucosa?
Only IgA1 and IgA2
42
What is CVID also known as?
Hypogammaglobulinaemia
PATH30001 - Mechanisms of Disease
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