Bofill M, Akbar A N, Salmon M, Robinson M, Burford G, Janossy G
Department of Clinical Immunology, Royal Free Hospital and School of Medicine, London, UK.
J Immunol. 1994 Jun 15;152(12):5613-23.
A subset of resting T cells expressing low levels CD45RA and CD45RO molecules (< 1 x 10(3)/cell; CD45RA(low)CD45RO(low)) but high levels of CD45RB and CD38 (5 to 25 x 10(3)/cell) were identified in human cord blood. When these CD45RA(low)RO(low) cells were isolated, they failed to survive in culture (< 10% viability at day 3) unless they were co-cultured on fibroblast monolayers. During the co-culture with fibroblasts, these lymphocytes acquired high levels of cytoplasmic and then membrane CD45RA by day 3 without signs of activation. When stimulated with PHA in the absence of fibroblasts the CD45RA(low)RO(low) cells required monocytes or IL-1 to respond; they rapidly perished if neither were present. On optimal mitogenic stimulation for 48 h in the presence of monocytes, > 90% of CD45RA(low)RO(low) T cells showed only transient CD45RA expression and rapidly acquired CD45RO reactivity. After activation for 48 h the stimulated CD45RA(low)RO(low) subset synthesized high levels of IL-2, comparable to mature peripheral T cells. No IL-4 was detected in these stimulated cultures of cord blood T cells. These data taken together suggest that CD45RA(low)RO(low) T cells in the cord blood are the relatively immature antecedents of CD45RA+RO T cells that require stromal factors for survival in a resting state. The same cells need monocytes or IL-1 for their activation to develop after a short CD45RA+ stage into activated CD45RO+RA(low) T cells with potent IL-2 biosynthetic capacity. An additional study of these cells is warranted to confirm that they are in fact the recent emigrants from the thymus, as suggested by similar observations in animal models.
在人脐带血中鉴定出一部分静息T细胞，其表达低水平的CD45RA和CD45RO分子（<1×10³/细胞；CD45RA低CD45RO低），但CD45RB和CD38水平较高（5至25×10³/细胞）。当分离出这些CD45RA低RO低细胞时，它们在培养中无法存活（第3天存活率<10%），除非与成纤维细胞单层共培养。在与成纤维细胞共培养期间，这些淋巴细胞在第3天时获得高水平的细胞质然后膜CD45RA，且无激活迹象。在无成纤维细胞的情况下用PHA刺激时，CD45RA低RO低细胞需要单核细胞或IL-1才能做出反应；如果两者都不存在，它们会迅速死亡。在单核细胞存在的情况下进行最佳促有丝分裂刺激48小时后，>90%的CD45RA低RO低T细胞仅显示短暂的CD45RA表达，并迅速获得CD45RO反应性。激活48小时后，受刺激的CD45RA低RO低亚群合成高水平的IL-2，与成熟外周T细胞相当。在这些脐带血T细胞的刺激培养物中未检测到IL-4。这些数据综合表明，脐带血中的CD45RA低RO低T细胞是CD45RA+RO T细胞相对不成熟的前体细胞，它们在静息状态下需要基质因子才能存活。相同的细胞在短暂的CD45RA+阶段后需要单核细胞或IL-1来激活，以发育为具有强大IL-2生物合成能力的活化CD45RO+RA低T细胞。对这些细胞进行进一步研究是必要的，以证实它们实际上是来自胸腺的近期迁出者，动物模型中的类似观察结果表明了这一点。
