Presenter of 1 Presentation
LOW CTLA-4 EXPRESSION BY NBEAL2 DEFICIENT CONVENTIONAL T CELLS AND IMMUNE DYSREGULATION IN GRAY PLATELET SYNDROME.
Abstract
Background and Aims
Recessive mutations in the NBEAL2 gene lead to gray platelet syndrome (GPS), a bleeding disorder characterized by macrothrombocytopenia and α-granule-deficient platelets. A proportion of NBEAL2-deficient patients present immune system abnormalities (autoimmune disease, autoantibodies, leukopenia, etc) – suggesting a role for NBEAL2 in immune homeostasis and tolerance. And the mechanism behind the development of autoimmunity remains unclear.
Methods
NBEAL2 role in primary human T cells was investigated by mass spectrometry interactome study, CRISPR-Cas-9 knock-down and single-cell RNA sequencing.
Results
In a mass spectrometry interactome study, 76 NBEAL2 partners were found in primary T cells, including LRBA (a member of the BEACH family, like NBEAL2). Recessive LRBA mutations cause autoimmunity and lymphocytic infiltration through defective CTLA-4 trafficking. We found that NBEAL2 deficiency leads to low CTLA-4 expression in patients’ effector T cells but not in their regulatory T cells. The NBEAL2-LRBA-CTLA-4 interaction was confirmed by immunoprecipitation. NBEAL2 knock-down in primary T cells also led to low CTLA-4 expression. Lastly, single cell RNAseq analyses of NBEAL2 and LRBA deficient lymphocytes uncovered an elevated IL6-STAT3 signature in LRBA patients, possibly reflecting their low CTLA-4 expression in regulatory T cells.
Conclusions
Our results show that NBEAL2 is involved in the regulation of CTLA-4 expression in conventional T cells and provide a molecular rationale for considering CTLA-4-immunoglobulin therapy in patients with GPS and autoimmune disease.