Engraftment Kinetics After Nonmyeloablative Allogeneic Peripheral Blood Stem Cell Transplantation: Full Donor T-Cell Chimerism Precedes Alloimmune Responses

Abstract

Nonmyeloablative allogeneic stem cell transplantation has recently been explored as a safer alternative to conventional high-dose transplant regimens. Although a high incidence of mixed chimerism after nonmyeloablative procedures has been reported, the exact kinetics of engrafting donor cells in specific cellular lineages has yet to be defined. We investigated lineage-specific chimerism in 15 patients receiving an allogeneic peripheral blood stem cell (PBSC) transplant from an HLA-identical (n = 14) or a 5/6 antigen-matched sibling donor after a preparative regimen of cyclophosphamide and fludarabine. Donor chimerism was assessed weekly in T lymphocytes and myeloid cells by polymerase chain reaction (PCR) of minisatellite regions. Eight patients survived between 121 to 409 days after transplant. Ten of 14 patients surviving more than 30 days (71.4%) had delayed disease regression consistent with a graft-versus-malignancy (GVM) effect. One patient rejected the transplant with subsequent recovery of autologous hematopoiesis. Hematological recovery was rapid (median, 11 days to ≥500 neutrophils/μL) and was initially predominantly recipient in origin. Donor myeloid chimerism gradually supplanted recipient hematopoiesis and became fully donor in all survivors by 200 days after transplantation. In contrast, T-cell engraftment was more rapid, with full chimerism in 7 patients by day 30 and in 6 further patients by day 200 after cyclosporine withdrawal and donor lymphocyte infusion. Full donor T-cell engraftment preceded donor myeloid engraftment, acute graft-versus-host disease, and disease regression, consistent with a requirement for 100% donor T-cell chimerism for full expression of the alloresponse. These results emphasize the importance of lineage-specific chimerism analysis to successfully manipulate engraftment after nonmyeloablative allogeneic PBSC transplantation.

Ex vivo evaluation of PBMNCs collected with a new cell separator

“…This study reports on our further evaluation of the ability of this device and the integral MNC software program to collect a variety of MNCs that can subsequently be separated into subsets by appropriate cell‐sorting techniques. Efficient collection of purified MNCs is becoming more important therapeutically, with the expanding role of MNCs in clinical practice 1–16 . Optimizing the CE and the quantity and purity of cells obtained by apheresis is a problem often compounded by concerns over the decreasing availability of apheresis donors and the decreasing time available for a healthy volunteer donor to devote to an apheresis collection.…”

“…They are also used for treating posttransplant EBV‐positive lymphoma and CMV infections 6,9–11 . Additional indications for DLI include control of GVHD and conservation of the graft‐versus‐leukemia effect, 12 promotion of graft‐versus‐malignancy, 13–15 and displacement of residual host HPCs in recurrent sickle cell anemia after allogeneic BMT 16 . Dendritic cells (DCs) are considered to be the most efficient antigen‐presenting cells and the most potent for initiation of the immune response.…”

Acute GVHD is a strong predictor of full donor CD3+ T cell chimerism after reduced intensity conditioning allogeneic stem cell transplantation

“…Quantitative analysis of chimerism by determination of the ratio of donor to recipient's cells is used to monitor the post‐transplantation period and could potentially determine the relapse of the underlying disease as early possible [6, 7]. Different methods are available including restriction fragment length polymorphism [8, 9], interphase fluorescence in situ hybridization (FISH) in the case of sex mismatched Allo‐SCT [10–13], polymerase chain reaction (PCR) for short‐tandem‐repeats (STR) or variable number tandem repeats [9, 14], and finally real‐time quantitative PCR (RQ‐PCR) for donor‐ and recipient‐specific polymorphisms [15–17].…”

Despite Inhibition of Hematopoietic Progenitor Cell Growth In Vitro, the Tyrosine Kinase Inhibitor Imatinib Does Not Impair Engraftment of Human CD133 + Cells into NOD/SCIDβ2m Null Mice

“…It is generally accepted that, after allogeneic hematopoietic cell transplantation (HCT), cure of CML and Philadelphia chromosome‐positive ALL depends on the contribution of the graft‐versus‐leukemia (GVL) effect [14, , –17]. This notion prompted the development of allogeneic transplantation after reduced‐intensity [18, –20] or truly nonmyeloablative conditioning [21, , , , , –27]. In these approaches, the conditioning regimen is substantially reduced, and reliance is placed on GVL effects for eradicating host leukemic cells [28].…”