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I&I WC2 > Immunodeficiencies > Flashcards

Immunodeficiencies Flashcards

1
Q

What is the purpose of DNA repair?

A

Prevent the formation of cancer

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2
Q

Which three immunological processes require DNA repair?

A
  1. V(D)J recombination
  2. SHM
  3. CSR
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3
Q

What are the different mechanisms of DNA repair? (4)

A
  1. Base excision repair (BER)
  2. Mismatch repair (MMR)
  3. Nucleotide excision repair (GG- and TC-NER)
  4. Double strand break repair (NHEJ, homologous)
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4
Q

Which DNA repair mechanism is used for abasic sites?

A

BER

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5
Q

Which DNA repair mechanism is used for replication errors?

A

MMR

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6
Q

Which DNA repair mechanism is used for bulky adducts/intrastrand crosslink?

A

Nucleotide excision repair

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7
Q

Which DNA repair mechanism is used for double strand break/interstrand crosslinks?

A

NHEJ, HR

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8
Q

For which immune cell types is DNA repair crucial? (2)

A
  1. B cells
  2. T cells
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9
Q

Which DNA repair pathway is involved in the DNA repair during V(D)J recombination?

A

NHEJ

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10
Q

Which DNA repair pathways are involved in the DNA repair during somatic hypermutation? (2)

A
  1. Base excision repair
  2. Mismatch repair
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11
Q

Which DNA repair pathways are involved in the DNA repair during class switch recombination? (2)

A
  1. NHEJ
  2. UNG
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12
Q

What are the three phases of V(D)J recombination?

A
  1. Initiation
  2. Hairpin opening
  3. Processing/ligation
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13
Q

Which proteins are involved in the initiation phase of V(D)J recombination? Leads to?

A

Rag 1/2 (only expressed in B and T cells during VDJ) -> cause DNA damage

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14
Q

Which proteins are involved in hairpin opening phase of V(D)J recombination? (2)

A
  1. DNA-PKcs
  2. Artemis
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15
Q

Which proteins are involved in the processing/ligation phase of V(D)J recombination? (3)

A
  1. LIG4
  2. XLF
  3. XRCC4
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16
Q

What is the function of the enzyme TdT?

A

Adds random nucleotides to increase junctional diversity (lymphoid specific)

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17
Q

What disease occurs if there is a defect in the process of V(D)J recombination?

A

You don’t make antigen receptors -> no T cells -> Severe combined immunodeficiency (SCID)

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18
Q

Describe the clinical presentation of SCID (6)

A
  1. Early onset (>3 months of age)
  2. Repeated/severe/opportunistic infections
  3. Failure to thrive
  4. Chronic diarrhea
  5. Lymphocytopenia
  6. Hypo-/agammaglobulinaemia
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19
Q

To what does a complete block of V(D)J recombination lead?

20
Q

What are the two types of T-B-SCID?

A
  1. Non-radiosensitive
  2. Radiosensitive
21
Q

How is non-radiosensitive T-B-SCID caused?

A

Defect in lymphoid specific initiation phase -> mutation in RAG1/RAG2

22
Q

Do you see neurological and other abnormalities in patients with RAG deficiency?

23
Q

How is radiosensitive T-B-SCID caused?

A

Defect in non-homologous end joining -> mutation in component NHEJ

24
Q

What determines the level of radiosensitivity in radiosensitive T-B-SCID patients?

A

Which defect you have -> Artemis for example not very sensitive, but ligation defect much more sensitive

25
Why is it important to know whether patients are sensitive to radiation? (2)
1. BTx 2. Medical exams
26
To what does an incomplete block of V(D)J recombination lead?
Spectrum of disease including atypical SCID, Omenn syndrome and primordial dwarfism
27
Do patients with a defect in NHEJ only have an immunological defect?
No -> all other cells of the body have this problem
28
What are the steps of the pathway to signaling for broken DNA ends? (3)
1. MRN complex 2. MRN recruits ATM (signaling hub) 3. ATM recruits more factors -> 53PB1
29
What encompasses ATM as a signaling hub? (2)
1. Signals for repair 2. Signals for shutdown of proliferation
30
Which syndromes can occur when you have defects in the pathway to signal for broken DNA ends? (2)
1. Nijmegen breakage syndrome 2. Ataxia Telangiectasia
31
What are the clinical characteristics of Nijmegen breakage syndrome? (7)
1. Facial appearance 2. Microcephaly 3. Growth retardation 4. Strong predisposition to malignancies 5. Immunodeficiency 6. High sensitivity for ionizing radiation 7. Biallelic mutations in NBN
32
True or false: Nijmegen breakage syndrome patients have reduced T and B cells, but not as low as SCID patients
True
33
When you can't keep the DNA ends together, you get?
Loss of juxtaposition of RAG-induced breaks
34
What are the clinical characteristics of Alexia Telangiectasia? (6)
1. Cerebellar deterioration/ataxia 2. Telangiectasia 3. Strong predisposition to malignancies 4. Variable immunodeficiency 5. Severe sensitivity for ionizing radiation 6. Biallelic mutations in ATM gene
35
What is the purpose of somatic hypermutation?
Affinity maturation -> selection for antigen binding
36
Where do the somatic hypermutations occur in the B cell?
Random mutations in the variable domain of the BCR --> CDRs
37
What are the two outcomes of somatic hypermutation?
1. Antigen-binding disrupted 2. Antigen-binding retained/increased
38
SHM and CSR both depend on..?
AID lesions
39
What is AID?
Activation-induced Cytidine Deaminase --> enzyme that introduces NICS
40
True or false: In SHM, DNA is repaired in a sloppy way
True -> few regions, single strand breaks
41
Which DNA repair pathways occur in SHM?
1. Base excision repair 2. Mismatch repair --> depending on the type of mutations
42
What does AID do to the amino acid C?
Deamination to U --> if you take out the uracil you get an abasic site
43
How does AID work during CSR?
AID makes lesions in switch regions (repetitive) -> lots of lesions/abasic sites -> dsDNA break
44
What is UNG deficiency?
Hyper IgM syndrome type 5
45
What are the characteristics of UNG deficiency? (4)
1. Susceptibility to bacterial infections 2. Normal or increased IgM 3. IgG, IgA, and IgE are low or absent 4. Defect in CSR
46
Why can patients with DNA repair defect also present with non-immunological features?
DNA repair is also important for brain development

I&I WC2 (16 decks)

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