Artificial thymic organoids represent a reliable tool to study T-cell differentiation in patients with severe T-cell lymphopenia.
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.
Bosticardo, M; Pala, F; Calzoni, E; Delmonte, OM; Dobbs, K; Gardner, CL; Sacchetti, N; Kawai, T; Garabedian, EK; Draper, D; Bergerson, JRE; DeRavin, SS; Freeman, AF; Güngör, T; Hartog, N; Holland, SM; Kohn, DB; Malech, HL; Markert, ML; Weinacht, KG; Villa, A; Seet, CS; Montel-Hagen, A; Crooks, GM; Notarangelo, LD
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