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Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations

Lookup NU author(s): Professor Sophie Hambleton

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Abstract

© 2017 by The American Society of Hematology. Heterozygous CTLA-4 deficiency has been reported as a monogenic cause of common variable immune deficiency with features of immune dysregulation. Direct mutation in CTLA-4 leads to defective regulatory T-cell (Treg) function associated with impaired ability to control levels of the CTLA-4 ligands, CD80 and CD86. However, additional mutations affecting the CTLA-4 pathway, such as those recently reported for LRBA, indirectly affect CTLA-4 expression, resulting in clinically similar disorders. Robust phenotyping approaches sensitive to defects in the CTLA-4 pathway are therefore required to inform understanding of such immune dysregulation syndromes. Here, we describe assays capable of distinguishing a variety of defects in the CTLA-4 pathway. Assessing total CTLA-4 expression levels was found to be optimal when restricting analysis to the CD45RA-Foxp3+ fraction. CTLA-4 induction following stimulation, and the use of lysosomal-blocking compounds, distinguished CTLA-4 from LRBA mutations. Short-term T-cell stimulation improved the capacity for discriminating the Foxp3+ Treg compartment, clearly revealing Treg expansions in these disorders. Finally, we developed a functionally orientated assay to measure ligand uptake by CTLA-4, which is sensitive to ligand-binding or -trafficking mutations, that would otherwise be difficult to detect and that is appropriate for testing novel mutations in CTLA-4 pathway genes. These approaches are likely to be of value in interpreting the functional significance of mutations in the CTLA-4 pathway identified by gene-sequencing approaches.

Publication metadata

Author(s): Hou TZ, Verma N, Wanders J, Kennedy A, Soskic B, Janman D, Halliday N, Rowshanravan B, Worth A, Qasim W, Baxendale H, Stauss H, Seneviratne S, Neth O, Olbrich P, Hambleton S, Arkwright PD, Burns SO, Walker LSK, Sansom DM

Publication type: Article

Publication status: Published

Journal: Blood

Year: 2017

Volume: 129

Issue: 11

Pages: 1458-1468

Print publication date: 16/03/2017

Online publication date: 16/03/2017

Acceptance date: 27/01/2017

ISSN (print): 0006-4971

ISSN (electronic): 1528-0020

Publisher: American Society of Hematology

URL: https://doi.org/10.1182/blood-2016-10-745174

DOI: 10.1182/blood-2016-10-745174

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