AUTHOR=Pille Melissa , Avila John , Sanchez Guillem Sanchez , Goetgeluk Glenn , De Munter Stijn , Jansen Hanne , Billiet Lore , Weening Karin , Xue Haipeng , Bonte Sarah , Ingels Joline , De Cock Laurenz , Pascal Eva , Deseins Lucas , Kerre Tessa , Taghon Tom , Leclercq Georges , Vermijlen David , Davis Brian , Vandekerckhove Bart TITLE=The Wiskott–Aldrich syndrome protein is required for positive selection during T-cell lineage differentiation JOURNAL=Frontiers in Immunology VOLUME=14 YEAR=2023 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1188099 DOI=10.3389/fimmu.2023.1188099 ISSN=1664-3224 ABSTRACT=

The Wiskott–Aldrich syndrome (WAS) is an X-linked primary immune deficiency caused by a mutation in the WAS gene. This leads to altered or absent WAS protein (WASp) expression and function resulting in thrombocytopenia, eczema, recurrent infections, and autoimmunity. In T cells, WASp is required for immune synapse formation. Patients with WAS show reduced numbers of peripheral blood T lymphocytes and an altered T-cell receptor repertoire. In vitro, their peripheral T cells show decreased proliferation and cytokine production upon aCD3/aCD28 stimulation. It is unclear whether these T-cell defects are acquired during peripheral activation or are, in part, generated during thymic development. Here, we assessed the role of WASp during T-cell differentiation using artificial thymic organoid cultures and in the thymus of humanized mice. Although CRISPR/Cas9 WAS knockout hematopoietic stem and progenitor cells (HSPCs) rearranged the T-cell receptor and differentiated to T-cell receptor (TCR)+ CD4+ CD8+ double-positive (DP) cells similar to wild-type HSPCs, a partial defect in the generation of CD8 single-positive (SP) cells was observed, suggesting that WASp is involved in their positive selection. TCR repertoire analysis of the DP and CD8+ SP population, however, showed a polyclonal repertoire with no bias toward autoreactivity. To our knowledge, this is the first study of the role of WASp in human T-cell differentiation and on TCR repertoire generation.