Wang X N, Sviland L, Ademokun A J, Dunn J, Cavanagh G, Proctor S J, Dickinson A M
Department of Haematology, School of Clinical and Laboratory Sciences, University of Newcastle, Newcastle-upon-Tyne, United Kingdom.
Transplantation. 1998 Oct 15;66(7):903-9. doi: 10.1097/00007890-199810150-00015.
Recent clinical data have demonstrated the success of allogeneic stem cell transplantation using HLA-mismatched unrelated human umbilical cord blood (CB). The incidence and severity of acute graft-versus-host disease (GVHD) in these mainly pediatric transplants is low. The immunological mechanisms by which CB transplants may result in reduced GVHD is not completely clear. In this study, the functional cellular alloreactivity of CB cells was investigated, by measuring the frequency of alloreactive helper and cytotoxic T lymphocyte precursors (HTLp and CTLp, respectively) in CB and detecting the ability of CB cells to induce graft-versus-host (GVH) type alloreactivity in vitro.
A human skin explant model was used to measure GVH type alloreactivity in vitro. A combined limiting dilution assay was carried out in parallel to determine alloreactive HTLp and CTLp frequencies. The cellular alloreactivity was compared between cord and HLA-haploidentical parental blood cells against the same HLA-mismatched unrelated stimulator.
The results demonstrated that alloreactive CTLp frequency in CB mononuclear cells (CBMCs) was significantly lower (mean, 1:35,694, range, 1:1,667-<1:500,000) than that in adult peripheral blood mononuclear cells (PBMCs) (mean, 1:5,333, range, 1:544-1:47,619). Alloreactive HTLp frequencies, however, were comparable for CBMCs and PBMCs (mean, 1:7,586, range, 1:1,359-1:200,000; and mean, 1:5,976, range, 1:385-1:50,000, respectively). A significantly decreased ability to induce in vitro GVH type alloreactivity was observed for CBMCs and that was strongly associated with low alloreactive CTLp frequencies (P=0.001).
The present study provides the first clear in vitro evidence to suggest that CBMCs are less able than PBMCs to induce skin GVH type alloreactivity in HLA-mismatched pairs. The severity of in vitro GVH type alloreactivity (graded as I-IV) was strongly associated with the levels of alloreactive CTLp frequencies. The low cellular alloreactivity of CBMCs detected in vitro suggests that in a proportion of cases HLA-mismatched unrelated CB may not give rise to severe GVHD in vivo after transplantation.
最近的临床数据表明，使用人类HLA错配的无关脐血（CB）进行异基因干细胞移植取得了成功。这些主要针对儿童的移植中，急性移植物抗宿主病（GVHD）的发生率和严重程度较低。CB移植可能导致GVHD降低的免疫机制尚不完全清楚。在本研究中，通过测量CB中同种异体反应性辅助性和细胞毒性T淋巴细胞前体（分别为HTLp和CTLp）的频率，并检测CB细胞在体外诱导移植物抗宿主（GVH）型同种异体反应的能力，对CB细胞的功能性细胞同种异体反应性进行了研究。
使用人皮肤外植体模型在体外测量GVH型同种异体反应性。同时进行联合极限稀释试验以确定同种异体反应性HTLp和CTLp频率。比较脐血和HLA单倍型相同的亲代血细胞针对相同HLA错配的无关刺激物的细胞同种异体反应性。
结果表明，CB单个核细胞（CBMCs）中同种异体反应性CTLp频率（平均值为1:35,694，范围为1:1,667 - <1:500,000）显著低于成人外周血单个核细胞（PBMCs）（平均值为1:5,333，范围为1:544 - 1:47,619）。然而，CBMCs和PBMCs的同种异体反应性HTLp频率相当（分别为平均值1:7,586，范围为1:1,359 - 1:200,000；以及平均值1:5,976，范围为1:385 - 1:50,000）。观察到CBMCs诱导体外GVH型同种异体反应的能力显著降低，且这与低同种异体反应性CTLp频率密切相关（P = 0.001）。
本研究提供了首个明确的体外证据，表明在HLA错配的配对中，CBMCs诱导皮肤GVH型同种异体反应的能力低于PBMCs。体外GVH型同种异体反应的严重程度（分级为I - IV级）与同种异体反应性CTLp频率水平密切相关。体外检测到的CBMCs低细胞同种异体反应性表明，在一部分病例中，HLA错配的无关CB在移植后体内可能不会引发严重的GVHD。
