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Blood. 2017 Mar 16;129(11):1458-1468. doi: 10.1182/blood-2016-10-745174. Epub 2017 Feb 3.

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

Author information

1
Institute of Immunity and Transplantation, Division of Infection & Immunity, School of Life and Medical Sciences, University College London, Royal Free Hospital, London, United Kingdom.
2
Immunology Department, Great Ormond Street Hospital for Children National Health Service (NHS) Foundation Trust, London, United Kingdom.
3
Papworth and Addenbrooke's Hospital NHS Foundation Trusts, Cambridge, United Kingdom.
4
Clinical Immunology Department, Royal Free Hospital, London, United Kingdom.
5
Sección de Infectología e Inmunopatología, Unidad de Pediatría, Hospital Virgen del Rocío/Instituto de Biomedicina de Sevilla (IBiS), Sevilla, Spain.
6
Primary Immunodeficiency Group, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; and.
7
Department of Immunology, University of Manchester, Royal Manchester Children's Hospital, Manchester, United Kingdom.

Abstract

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.

PMID:
28159733
PMCID:
PMC5438243
DOI:
10.1182/blood-2016-10-745174
[Indexed for MEDLINE]
Free PMC Article

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