Lineage-specific chimaerism after stem cell transplantation in children following reduced intensity conditioning: potential predictive value of NK cell chimaerism for late graft rejection

Abstract

Chimaerism of FACS-sorted leucocyte subsets (CD14 þ , CD15 þ , CD3À/56 þ , CD3 þ /4 þ , CD3 þ /8 þ , CD19 þ ) was monitored prospectively between days þ 14 and þ 100 in 39 children undergoing allogeneic stem cell transplantation with reduced intensity-conditioning regimens. Cell subsets exceeding 1% of nucleated cells were subject to cell sorting. Chimaerism was analysed by dual-colour FISH and/or by short tandem repeat-polymerase chain reaction. The chimaerism pattern on day þ 28 was evaluated with regard to its correlation with graft rejection. Of 39 patients, nine patients had donor chimaerism (DC) in all subsets. Mixed/recipient chimaerism (MC/RC) was detectable within T cells in 62%, within NK cells in 39% and within monocytes and granulocytes in 38% of the patients. The correlation of secondary graft rejection with the chimaerism pattern on day þ 28 revealed the strongest association between RC in NK-cells (Po0.0001), followed by T cells (P ¼ 0.001), and granulocytes and monocytes (P ¼ 0.034). Notably, patients with RC in T cells rejected their graft only if MC or RC was also present in the NK-cell subset. By contrast, none of the children with DC in NK cells experienced a graft rejection. These observations suggest that, in the presence of recipient T-cell chimaerism, the chimaerism status in NK-cells on day þ 28 might be able to identify patients at high risk for late graft rejection.

The EuroChimerism concept for a standardized approach to chimerism analysis after allogeneic stem cell transplantation

“…1,4,23 When rare cell subsets are isolated for subsequent chimerism analysis, the availability of sufficient amounts of DNA may become a limiting factor with regard to the achievable sensitivity and reproducibility of results. The experience among members of the EUC consortium indicated that the cell number available for analysis in these instances can be as low as a few hundred to a few thousand cells.…”

Increasing mixed chimerism and the risk of graft loss in children undergoing allogeneic hematopoietic stem cell transplantation for non-malignant disorders

“…4,11,15 Andreani et al 13 showed an 84% rejection rate in patients with thalassemia who had 425% autologous cells in WB at 2 months post transplant, and Baron et al 1,2 and Matthes-Martin et al 5 showed that low donor CD3 þ and natural killer cell chimerism at days 14 and 28 post transplant correlated with graft rejection. Long-term follow-up of patients with thalassemia showed that once tolerance to donor cells has been established, graft rejection does not occur even at low levels (o10%) of donor WB engraftment.…”

“…The study included 24 children (median age 7.6 years, range (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)) undergoing first unmodified allogeneic HSCT for a non-malignant disorder at University of California, San Francisco, (UCSF) Children's Hospital, Pediatric Blood and Marrow Transplant Unit (PBMTU) between January 2001 and March 2007. Only patients who received fludarabine-or cyclophosphamide-based conditioning regimen and had chimerism testing done by the STR technique were included.…”

“…1,2,5 Graft function. The graft was considered functional if it resulted in correction of the underlying disease.…”

“…1,2 Mixed chimerism (MC) is related to increased risk of relapse in patients with acute leukemia, and low levels of donor CD3 þ and natural killer cell chimerism correlate with an increased risk of graft rejection. [3][4][5] However, the presence of MC is associated with a decreased incidence of acute graft-versus-host disease (aGVHD). 6 Myeloablative conditioning more commonly eradicates the recipient's hematopoietic cells and results in complete donor hematopoietic chimerism, whereas reduced intensity or non-myeloablative conditioning regimens frequently result in MC.…”