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Effects of deoxyadenosine on the activation of ADA inhibited T & B cells
Insights
Deoxyadenosine inhibits T cell proliferation in adenosine deaminase deficiency (ADA-SCID). Prostaglandin E1 exacerbates this, suggesting cyclic nucleotide issues contribute to T lymphopaenia in ADA-SCID.
Area of Science:
- Immunology
- Biochemistry
Background:
- Adenosine deaminase deficiency (ADA-SCID) causes severe combined immunodeficiency.
- Elevated deoxyadenosine levels in ADA-SCID are implicated in T cell dysfunction.
Purpose of the Study:
- To investigate the inhibitory effects of deoxyadenosine on T lymphocyte proliferation in an in vitro model of ADA deficiency.
- To explore the role of cyclic nucleotide metabolism in T lymphopaenia associated with ADA-SCID.
Main Methods:
- Utilized an in vitro model simulating adenosine deaminase deficiency.
- Assessed T lymphocyte proliferation triggered by phytohemagglutinin (PHA).
- Examined the influence of Prostaglandin E1 on T cell sensitivity to deoxyadenosine.
Main Results:
- Deoxyadenosine inhibited PHA-induced T lymphocyte proliferation at concentrations relevant to ADA-SCID.
- Prostaglandin E1 enhanced T cell sensitivity to deoxyadenosine-mediated inhibition.
- ADA-inhibited B cell proliferation and Ig synthesis showed variable sensitivity to deoxyadenosine.
Conclusions:
- Derangements in cyclic nucleotide metabolism may underlie T lymphopaenia in ADA-SCID.
- Deoxyadenosine's inhibitory effects on T cells are significant in ADA-SCID.
- Variability in B cell responses suggests modulation by other cells in ADA-SCID patients.
Abstract:
Using an in vitro model of adenosine deaminase deficiency, we have shown that the triggering of T lymphocyte proliferation by PHA is inhibited by concentrations of deoxyadenosine likely to occur in the plasma of ADA deficient children with severe combined immunodeficiency (ADA-SCID). Prostaglandin E1 increases the sensitivity of T cells to this inhibition, suggesting that derangement of cyclic nucleotide metabolism underlies the profound T lymphopaenia seen in ADA-SCID and in patients treated with the ADA inhibitor, deoxycoformycin. The proliferation and Ig synthesis of ADA inhibited B cells stimulated with protein A and EBV is in general less sensitive to the inhibitory effects of deoxyadenosine. However, this sensitivity varies widely between experiments suggesting that other cells present in the cultures may modify the inhibitory effect of deoxyadenosine. This may help explain the variability in B cell numbers and function in patients with ADA-SCID.