The Role of Selective Depletion of Alloreactive Donor T Cells in Graft-Versus-Host Disease after Allogeneic Bone Marrow Transplantation.

One of the main goals in allogeneic bone marrow(BM) transplantation is the abrogation of graft-versus-host disease (GVHD) with the preservation of antileukemia and antiviral activity. The Study present a selective T cell depletion strategy based on the physical separation of the alloreactive T cells, which were identified by expression of two activation-induced antigens (CD25 and CD69). T cells from C57BL/6(H-2^b) mice were first activated with BALB/c (H-2^d) recipient spleen cells in a 2-day mixed-lymphocyte-culture (MLC). Following this activation, this compound is selectively depleted based on expression of two activation-induced antigens CD25 and CD69 using magnetic cell sorting. The depleted cells or the untreated cells were then rechallenged respectively in a secondary MLC, with the same stimulator cells or a third-party (DBA^H-2k) or tumor- specific (SP2/0, BALB/c-origin myeloma) cells. Cells proliferation were assayed at the indicated time points(1, 2, 3, 4, 5 days). These treated cells or control-cultured cells (2.0×10⁶) mixed with 5.0×10⁶ BM cells from C57BL/6 were transfused respectively by the trail vain into the lethally irradiated BALB/c to observe the survival time, GVHD incidence and pathological analysis. MLC assays demonstrated that this technique led to a significant decrease in alloreactivity of donor cells(29.02~64.17%), which at the same time preserved reactivity against third party cells(49.61~75.69%)and anti-tumor cells(61.14~68.62%). The mice in the group of control-coclutured were died of acute GVHD within 24days. The 7 recipient mice in the treated group were free of acute GVHD, and 3 mice were died of acute GVHD (aGVHD) within 23 days. MACS-based ex-vivo depletion of alloreactive donor T cells based on expression of two activation-induced antigens (CD25 and CD69) could inhibit anti-host responses, by contrast, anti-SP2/O and anti-third-party responses were preserved. Cotransplantation of these selected depleted cells and BM cells could reduce aGVHD.