Artificial thymic organoids represent a reliable tool to study T-cell differentiation in patients with severe T-cell lymphopenia
Marita Bosticardo, Francesca Pala, Enrica Calzoni, Ottavia M. Delmonte, Kerry Dobbs, Cameron L. Gardner, Nicolò Sacchetti, Tomoki Kawai, Elizabeth Garabedian, Debbie Draper, Jenna Bergerson, Suk See De Ravin, Alexandra F. Freeman, Tayfun Güngör, Nicholas Hartog, Steven M. Holland, Donald B. Kohn, Harry L. Malech, M. Louise Markert, Katja G. Weinacht, Anna Villa, Christopher S. Seet, Amélie Montel‐Hagen, Gay M. Crooks, Luigi D. Notarangelo
Abstract
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.