Hashem Hasan, Lazarus Hillard M
Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio.
Department of Medicine, Case Western Reserve University, Cleveland, Ohio.
Biol Blood Marrow Transplant. 2015 Apr;21(4):612-9. doi: 10.1016/j.bbmt.2014.09.003. Epub 2014 Sep 16.
Double umbilical cord blood transplantation (UCBT) was developed as a strategy to circumvent the cell dose limitation of single UCBT with a concomitant potential benefit of lowering the rate of leukemia relapse. Sustained hematopoiesis after double UCBT usually is derived from a single donor unit, as only a few patients have been reported to display stable mixed-unit chimerism for varying periods of time. Explanations for the 1 unit dominance, predictors for identifying unit superiority, and persistence of long-term mixed-unit chimerism remain elusive. Review of published literature revealed only 11 of 280 patients (4%) with mixed-unit chimerism for at least 1 year after transplantation, with 3 patients receiving reduced-intensity conditioning regimens. Mixed-unit chimerism was more likely if both units were closely HLA matched to each other. Outcome data for patients with stable mixed-unit chimerism, for the most part, were scarcely reported. Analysis of the small sample size revealed a potential advantage of stable mixed-unit chimerism on enhancing the graft-versus-leukemia effect; however, definitive conclusions cannot be made on the effect of mixed-unit chimerism on the rates of graft-versus-host disease. Therefore, gathering outcome data prospectively in larger clinical series will help answer the question of whether stable mixed-unit chimerism is either beneficial and, therefore, should be strived for, detrimental and, thus, needs to be eliminated, or if it is of no clinical consequence.
双份脐血移植（UCBT）作为一种策略而被开发出来，旨在规避单份UCBT的细胞剂量限制，并同时具有降低白血病复发率的潜在益处。双份UCBT后的持续造血通常源自单个供体单位，因为仅有少数患者被报道在不同时间段内显示出稳定的混合单位嵌合状态。关于单一单位优势的解释、识别单位优势的预测因素以及长期混合单位嵌合状态的持续性仍然不清楚。对已发表文献的回顾显示，在280例患者中，仅有11例（4%）在移植后至少1年出现混合单位嵌合状态，其中3例接受了减低强度预处理方案。如果两个单位彼此HLA匹配紧密，则更有可能出现混合单位嵌合状态。对于具有稳定混合单位嵌合状态患者的结局数据，在很大程度上几乎没有报道。对小样本量的分析揭示了稳定混合单位嵌合状态在增强移植物抗白血病效应方面的潜在优势；然而，关于混合单位嵌合状态对移植物抗宿主病发生率的影响，无法得出明确结论。因此，在更大的临床系列中前瞻性地收集结局数据，将有助于回答稳定混合单位嵌合状态是有益的（因此应努力实现）、有害的（因此需要消除），还是没有临床意义这一问题。
