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11 Cards in this Set
- Front
- Back
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What is deficient in X-linked SCIDS? What still works? Why?
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- absence of T cells and NK cells
- B cells present but do not function well - non functioning gamm c chain |
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What is deficient in Autosomal recessive SCIDS? What still works?
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- Absence of B and T cells
- NK cells still function |
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What is one of the most common types of autosomal recessive SCIDS?
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- Adenosine deaminase deficiency
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What is the role of adenosine deaminase?
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- enzyme of purine salvage pathway
- gives primary source of nucleotides |
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What happens when adenosine deaminase is deficient?
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- increase in dATP and ATP
- if dATP constitutes more than 1% of total ATP levels, DNA synthesis halts - Highest level of ADA activity is in thymus and lymph tx, so most profoundly affected (cause defective B and T cells) |
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Discuss Enzyme Replacement therapy in ADA deficiency
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- Added PEG to ADA which enables modified enzyme to remain in blood for 1-2 weeks and only reduces activity by 40%
- increases amount in circulation - tricks immune so there is no mounted attack against the bovine ADA |
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Discuss T cell gene therapy
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- easier to growth than hematopoietic stem cells
- Isolate from patients and culture with IL-2 - Insert ADA gene via retrovirus - select for Neo resistance (selective marker) - amplified - put back into patient - requires repeated treatments every 2-3 months |
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Discuss hematopoietic stem cell therapy for X-linked SCID
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- hematopoietic stem cells express CD-34 cells
Methods - harvest 1/2 pint of hematopoietic stem cells - isolate CD34 cells - partially wipe out old marrow (cyto reduction) - inject new marrow - isolate patient - takes weeks to replace and build up |
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What were problems with hematopoietic stem cell therapy for X-linked SCID?
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- 25% patients developed leukemia
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Describe the progression of treatments for SCID
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- heavy antibiotics
- bone marrow transplant - enzyme replacement therapy - gene therapy |
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Discuss the success of bone marrow transplant for ADA-SCID
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- HLA identical sibling 90%
- HLA haplo sibiling/relative 65% - HLA identical non-relative 50% |
