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Immunology and Haematology > Primary Immunodeficiency > Flashcards

Primary Immunodeficiency Flashcards

1
Q

Describe the development of immune cells?

A
  1. Begins as pluripotent stem cell
  2. Develops into 1 off
    1. Premyeloid cell (precursor for neutrophils)
    2. Lymphocyte-committed stem cell (precursors for T cells which develop in thymus, or B cells which develop in bone marrow)
    3. Premonocyte (precursor of monocytes, which then becomes macrophage)
  3. T cell can develop into: Helper cell (Th1 and Th2), Cytotoxic cell or memory cell
  4. B cells produce antibodies and become plasma cell
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2
Q

What kind of stem cell do immune cells begin as?

A

Pluripotent immune cell

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3
Q

What is the precursor for neutrophils?

A

Premyeloid cell

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4
Q

What is the precursor for T and B cells?

A

Lymphocyte-committed stem cell

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5
Q

What is the precursor for macrophages?

A

Premonocyte -> monocyte -> macrophage

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6
Q

What are the different kinds of immunity?

A
  • Specific immunity
    • Antibodies (through B cells)
    • Cellular immunity (through T cells and antigen presenting cells)
  • Non-specific immunity
    • Compliment system
    • Phagocytes
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7
Q

What cells are involved in specific immunity?

A
  • Antibodies (through B cells)
  • Cellular immunity (through T cells and antigen presenting cells)
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8
Q

What cells are involved in non-specific immunity?

A
  • Compliment system
  • Phagocytes
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9
Q

When your born, where do most of your antibodies come from and what kind are they?

A

When born most antibodies come from mother (IgG), but then develop own

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10
Q

Each kind of immunity provides defence against different microorganisms, describe this?

A
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11
Q

What are the 2 categories of immunodefiency diseases?

A
  • Primary (or congenital) immunodeficiency
  • Secondary (or acquired) immunodeficiency
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12
Q

What are some complications of immunodeficiency diseases?

A
  • Increased susceptibility to infection, cancer and possibly autoimmunity
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13
Q

What is primary immunodeficiency?

A

These are a collection of diseases

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14
Q

Describe the aetiology of primary immunodeficiency?

A
  • Genetic, congenital disorders
    • Caused by mutations or autoimmunity
  • Part of the immune system is missing or functioning abnormally
    • Abnormality could be
      • Component of innate immune system
      • Stages of lymphocyte development
        • The earlier in the process of development the more profound the effect
      • Responses of mature lymphocytes to antigenic stimulation
  • NOT secondary to other disease processes, toxins or drugs
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15
Q

Suspect immunodeficiency when infections are..?

A
  • Recurrent
  • Unusual microorganisms
  • Difficult to treat
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16
Q

What does the type of opportunistic infection give clues about?

A

Degree and cause of immunodeficiency

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17
Q

What opportunistic infections often occur in T cell defects?

A
  • T cells or macrophages – intracellular organisms such as protozoa, viruses and intracellular bacteria including mycobacteria
    • Such as mycobacterium tuberculosis causing lung infections in immunocompetent people, but can invade body outside lungs in immunocompromised
  • T cells – reactivation of latent herpesvirus, or herpesvirus-induced tumours (such as koposi sarcoma) and non-
    • TH17 - candida
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18
Q

What opportunistic infections occur in compliment defects?

A
  • Compliment system – meningitis caused by Neisseria meningitides
19
Q

What opportunistic infections occur in B cell defects?

A
  • Defective antibody production – encapsulated bacteria
    • Pneumococcus or haemophilus spp – antibody deficiency (IgG and IgA)
20
Q

What are possible causes of primary immunodeficiency?

A
  • Mutations
    • Permanent alteration in DNA sequence that affects a gene so it is no longer functional
    • Rarely affect immune system, causing severe disease when they do
  • Polymorphisms
    • Involves one of two or more variants of a particular DNA sequence
    • Commonly affects immune system, causing moderate increased risk for infection
  • Polygenic disorders
    • Caused by the combined action of more than one gene
    • Relatively commonly affect immune system and often affect antibodies, some of these conditions caused by autoimmunity
21
Q

What kind of immunodeficiency do mutations often result in?

A

Severe combined immunodeficiency (SCID)

22
Q

What is severe combined immunodeficiency?

A

Group of disorders that affect both T and B cells

23
Q

What does SCID stand for?

A

Severe combined immunodeficiency

24
Q

What is the treatment for SCID?

A

Stem cell transplant

25
Q

What are genetic polymorphisms?

A

Genetic polymorphisms are alleles (different forms) of the same gene occurring at a single locus in at least 1% of the population

26
Q

What are examples of genetic polymorphisms?

A
  • Human leukocyte antigen (HLA) alleles are polymorphic and affect outcome of infection
    • Individuals with HLA alleles that are unable to bind viral peptides have worse outcome
  • Mannan-binding lectin (MBL) binds to sugars in bacterial cell walls and activates classic complement pathway
    • Polymorphisms in this affect risk of infections
27
Q

What are examples of polygenic disorders?

A
  • Common variable immunodeficiency (CVID)
    • This is a group of diseases
  • IgA deficiency
  • Specific antibody deficiency
28
Q

What does CVID stand for?

A

Common variable immunodeficiency

29
Q

Describe the epidemiology of CVID (M:F, incidence)?

A
  • M:F 1:1
  • Incidence 1:20000 young people
  • Most common immunodeficiency requiring treatment
30
Q

What is seen in the biochemistry for CVID?

(levels of IgG, IgA, IgM, B and T cells)

A
31
Q

What are possible complications of CVID?

A
  • Recurrent respiratory tract infections
  • Infections that involves gut, skin and nervous system may occur
  • Autoimmunity is common
32
Q

What is the presentation of specific antibody deficiency?

A
  • Presentation with specific microorganisms despite normal total IgG
  • Do not respond to polysaccharide antigens and do not respond to vaccinations
33
Q

What is an example of a specific antibody deficiency?

A

An example is autoimmune polyendocrinopathy candidiasis ectodermal dysplasia (APECED)

34
Q

What does APECED stand for?

A

Autoimmune polyendocrinopathy candidiasis ectodermal dysplasia

35
Q

Describe the pathogenesis of APECED?

A
  • Defect in central tolerance and experience many types of autoimmunity
    • Some produce autoantibodies against IL-17 causing impaired responses to candida
    • Others produce antibodies against IFN-γ causing recurrent mycobacterial infection
36
Q

What does monogenic and polygenic mean?

A

Monogenic = mutation in single gene

Polygenic = mutation in many genes

37
Q

Describe the typical presentation, history and lymphocyte count for SCID?

A
  • Presentation
    • Defective T and B cells so develop infections in first few weeks of life
    • Unusual or recurrent infection
    • Diarrhoea
    • Unusual rashes
  • History
    • Family history of neonatal death
    • Family history of consanguinity (incest)
  • Lymphocyte count
    • Low count (less than 1x109/L
    • Measured by flow cytometry
38
Q

How is lymphocyte count measured?

A

Flow cytometry

39
Q

Describe the typical presentation and antibody levels for antibody deficiency?

A
  • Presentation
    • Later in life
    • Chronic or recurrent bacterial respiratory infection
  • Antibody levels
    • IgG, IgA and IgM should be measured
    • With low levels of immunoglobulin causes of secondary immunodeficiency should be excluded
    • If total Igs are normal, specific antibodies against Hemophilus spp. And pneumococcus measured
    • If these are normal, check no problems with complement or neutrophil function
40
Q

Describe the treatment of a primary immunodeficiency?

A

Aim is to prevent infection

Treatment options:

  • For mild immunodeficiency
    • Prophylactic antibiotics
  • For severe antibody deficiency
    • Immunoglobulin replacement therapy
41
Q

Describe the treatment of SCID?

A
  • Definitive treatment should be given, but until then
    • Avoid live vaccines
    • Prophylaxis against opportunist infections
  • Provide definitive treatment
    • Stem cell transplantation (SCT)
      • Most successful if done within a few weeks of birth
    • Or gene therapy if SCT not option
42
Q

What is gene therapy?

A

Gene therapy = uses recombinant technology to correct genetic defect in patients own stem cells, which can then reconstitute the immune system

43
Q

What criteria must be met for gene therapy to be successful?

A
  1. Genetic mutation identified, evidence correcting this will improve condition
  2. Transfected gene must confer a proliferation or survival advantage
  3. Must not cause malignancy

Immunology and Haematology (23 decks)

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