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Human In Vitro Suppression as Screening Tool for the Recognition of an Early State of Immune Imbalance
Published on: July 22, 2011
Quantitative reduction of the TCR adapter protein SLP-76 unbalances immunity and immune regulation
Owen M Siggs1, Lisa A Miosge2, Stephen R Daley2
1Department of Immunology, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia; Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom; owen.siggs@sanger.ac.uk chris.goodnow@anu.edu.au.
Abstract:
Gene variants that disrupt TCR signaling can cause severe immune deficiency, yet less disruptive variants are sometimes associated with immune pathology. Null mutations of the gene encoding the scaffold protein Src homology 2 domain-containing leukocyte protein of 76 kDa (SLP-76), for example, cause an arrest of T cell positive selection, whereas a synthetic membrane-targeted allele allows limited positive selection but is associated with proinflammatory cytokine production and autoantibodies. Whether these and other enigmatic outcomes are due to a biochemical uncoupling of tolerogenic signaling, or simply a quantitative reduction of protein activity, remains to be determined. In this study we describe a splice variant of Lcp2 that reduced the amount of wild-type SLP-76 protein by ~90%, disrupting immunogenic and tolerogenic pathways to different degrees. Mutant mice produced excessive amounts of proinflammatory cytokines, autoantibodies, and IgE, revealing that simple quantitative reductions of SLP-76 were sufficient to trigger immune dysregulation. This allele reveals a dose-sensitive threshold for SLP-76 in the balance of immunity and immune dysregulation, a common disturbance of atypical clinical immune deficiencies.
Insights
Reduced amounts of the scaffold protein SLP-76 (Src homology 2 domain-containing leukocyte protein of 76 kDa) can trigger immune dysregulation. This study reveals a dose-sensitive threshold for SLP-76 in maintaining immune balance.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Gene variants affecting T cell receptor (TCR) signaling can lead to immune deficiencies or pathology.
- The scaffold protein SLP-76 (Src homology 2 domain-containing leukocyte protein of 76 kDa) is crucial for TCR signaling, with null mutations causing severe immune defects.
- Previous studies suggest that the degree of TCR signaling disruption influences outcomes, but whether this is quantitative or qualitative remains unclear.
Purpose of the Study:
- To investigate the impact of quantitative reductions in SLP-76 protein levels on immune regulation.
- To determine if reduced SLP-76 activity is sufficient to cause immune dysregulation.
Main Methods:
- Generated a splice variant of the Lcp2 gene, significantly reducing wild-type SLP-76 protein levels (~90%).
- Analyzed the effects of this quantitative reduction on immunogenic and tolerogenic pathways in mutant mice.
- Assessed the production of cytokines, autoantibodies, and IgE in mutant mice.
Main Results:
- A ~90% reduction in SLP-76 protein disrupted both immunogenic and tolerogenic signaling pathways.
- Mutant mice exhibited excessive production of proinflammatory cytokines, autoantibodies, and IgE.
- These findings demonstrate that quantitative reductions in SLP-76 are sufficient to induce immune dysregulation.
Conclusions:
- A dose-sensitive threshold for SLP-76 exists, balancing immunity and immune dysregulation.
- Quantitative reductions in SLP-76 are sufficient to trigger autoimmune and inflammatory conditions.
- This provides insights into the pathogenesis of atypical clinical immune deficiencies characterized by immune dysregulation.
