Mechanisms of thymic repair and immune reconstruction of in vitro-induced precursor T cells as a modified haplo-identical HSCT regimen

Abstract

Purpose Diseases relapse and severe infection caused by delayed immune reconstitution are still challenges in the haplo-identical hematopoietic stem cell transplantation (haplo-HSCT). Non-myeloablative transplant regimens also only alleviated these complications and did not solve the above problems. Among them, the thymus damage caused by preconditioning including irradiation and chemotherapy and graft-versus-host disease (GVHD) is the primary issue. Accelerating the recovery of thymus-derived T cells after transplantation is a key to solving above problem.

Methods Therefore, we established a cell culture system using Notch ligand Delta4 and IL-7 that could induce and amplify hematopoietic stem cells differentiation and proliferation into precursor T (preT) cells in vitro. Non-myeloablative HSCT protocol was modified by using induced preT and G-CSF mobilized donor splenic mononuclear cells (MNC) co-infusion. Thymic GVHD, thymic repair, thymus-derived T cell development were compared in thymus-irradiated mice treated with MNC+preT and only MNC by polychromatic immunofluorescence tracking and T cell receptor Vβ detection.

Results The data showed that pre T cells highly expressed CC9 and RANKL markers restored thymic architecture, weakened GVHD effects, enhanced immuno-tolerance and accelerated immune reconstitution by activating the RANK/RANKL pathway.

Conclusion The modified non-myeloablative regimen containing preT cells will be more conducive to the widespread use of haplo-HSCT in clinical work.