Artificial thymic organoids represent a reliable tool to study T-cell differentiation in patients with severe T-cell lymphopenia

• Published in: Blood advances Vol. 4; no. 12; pp. 2611 - 2616
• Main Authors: Bosticardo, Marita, Pala, Francesca, Calzoni, Enrica, Delmonte, Ottavia M., Dobbs, Kerry, Gardner, Cameron L., Sacchetti, Nicolo', Kawai, Tomoki, Garabedian, Elizabeth K., Draper, Debbie, Bergerson, Jenna R.E., DeRavin, Suk See, Freeman, Alexandra F., Güngör, Tayfun, Hartog, Nicholas, Holland, Steven M., Kohn, Donald B., Malech, Harry L., Markert, Mary Louise, Weinacht, Katja G., Villa, Anna, Seet, Christopher S., Montel-Hagen, Amelie, Crooks, Gay M., Notarangelo, Luigi D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23.06.2020; American Society of Hematology
• Subjects: Antigens, CD34; Cell Differentiation; Hematopoiesis and Stem Cells; Hematopoietic Stem Cells; Humans; Lymphopenia; Organoids
• ISSN: 2473-9529; 2473-9537
• DOI: 10.1182/bloodadvances.2020001730

The study of early T-cell development in humans is challenging because of limited availability of thymic samples and the limitations of in vitro T-cell differentiation assays. We used an artificial thymic organoid (ATO) platform generated by aggregating a DLL4-expressing stromal cell line (MS5-hDLL4) with CD34+ cells isolated from bone marrow or mobilized peripheral blood to study T-cell development from CD34+ cells of patients carrying hematopoietic intrinsic or thymic defects that cause T-cell lymphopenia. We found that AK2 deficiency is associated with decreased cell viability and an early block in T-cell development. We observed a similar defect in a patient carrying a null IL2RG mutation. In contrast, CD34+ cells from a patient carrying a missense IL2RG mutation reached full T-cell maturation, although cell numbers were significantly lower than in controls. CD34+ cells from patients carrying RAG mutations were able to differentiate to CD4+CD8+ cells, but not to CD3+TCRαβ+ cells. Finally, normal T-cell differentiation was observed in a patient with complete DiGeorge syndrome, consistent with the extra-hematopoietic nature of the defect. The ATO system may help determine whether T-cell deficiency reflects hematopoietic or thymic intrinsic abnormalities and define the exact stage at which T-cell differentiation is blocked. •The ATO system allows precise definition of developmental blocks in patients with gene defects that cause T-cell lymphopenia.•The ATO system can help distinguish between hematopoietic autonomous and extra-hematopoietic defects that cause T-cell lymphopenia. [Display omitted]