Wolf M L, Weng W K, Stieglbauer K T, Shah N, LeBien T W
Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455.
J Immunol. 1993 Jul 1;151(1):138-48.
We have previously demonstrated that IL-7 can sustain the growth of normal human B cell precursors (BCP) for several weeks on bone marrow-derived stromal cells. Flow cytometric analysis of BCP recovered from IL-7 supplemented cultures revealed two- to threefold higher levels of cell surface CD19, compared with BCP maintained without IL-7. Short term culture of BCP showed that IL-7 enhancement of CD19 was dose-dependent, with increases detected by day 1 and plateauing by days 3 to 4. IL-7 increased cell-surface CD19 on small lymphoid cells, and to a greater degree on lymphoblasts, whereas cell-surface CD10 was unchanged. The CD34+/CD19+ pro-B cell population showed a greater increase in cell-surface CD19 compared with pre-B and immature B cells. IL-1, IL-3, IL-4, IL-6, and stem-cell factor had no effect on CD19. The potential functional significance of IL-7-enhanced cell-surface CD19 was examined using a F(ab')2 fragment of anti-CD19. This reagent had no effect on [3H]TdR incorporation in BCP cultured in the absence or presence of IL-7 for 5 days, but homotypic adhesion of BCP was induced at a concentration as low as 1.0 ng/ml F(ab')2 anti-CD19. IL-7 enhanced the F(ab')2 anti-CD19 induced homotypic adhesion of BCP in a dose-dependent manner. Blocking antibody studies indicated that members of the beta 1 or beta 2 integrin families did not mediate anti-CD19-induced homotypic adhesion, even though the adhesion was completely ablated by 10 mM EDTA. The pre-B and immature leukemic B cell lines NALM-6 and 1E8 expressed comparable levels of cell-surface CD19, and exhibited comparable increases after IL-7 stimulation. However, their homotypic adhesion responses to anti-CD19 were different. NALM-6 cells exhibited a strong homotypic adhesion response to anti-CD19 that was EDTA-resistant, and beta 1/beta 2 integrin independent. 1E8 cells only responded to anti-CD19 after IL-7 stimulation; this response was EDTA-sensitive and beta 1/beta 2 integrin independent. These collective results indicate that IL-7 not only acts as a growth factor for human BCP, but also regulates signal transduction through cell-surface CD19.
我们之前已经证明，白细胞介素-7（IL-7）能够在骨髓来源的基质细胞上维持正常人B细胞前体（BCP）生长数周。对从添加IL-7的培养物中回收的BCP进行流式细胞术分析发现，与未添加IL-7培养的BCP相比，细胞表面CD19水平高出两到三倍。BCP的短期培养表明，IL-7对CD19的增强作用呈剂量依赖性，在第1天即可检测到增加，至第3至4天达到平台期。IL-7增加了小淋巴细胞表面的CD19，对淋巴母细胞的作用更强，而细胞表面CD10则没有变化。与前B细胞和未成熟B细胞相比，CD34+/CD19+前B细胞群体表面CD19的增加更为明显。白细胞介素-1（IL-1）、白细胞介素-3（IL-3）、白细胞介素-4（IL-4）、白细胞介素-6（IL-6）和干细胞因子对CD19没有影响。使用抗CD19的F(ab')2片段研究了IL-7增强的细胞表面CD19的潜在功能意义。该试剂对在有无IL-7的情况下培养5天的BCP中[3H]TdR掺入没有影响，但在低至1.0 ng/ml F(ab')2抗CD19的浓度下即可诱导BCP的同型黏附。IL-7以剂量依赖性方式增强了F(ab')2抗CD19诱导的BCP同型黏附。阻断抗体研究表明，β1或β2整合素家族成员不介导抗CD19诱导的同型黏附，尽管10 mM乙二胺四乙酸（EDTA）可完全消除这种黏附。前B细胞和未成熟白血病B细胞系NALM-6和1E8表达相当水平的细胞表面CD19，在IL-7刺激后表现出相当程度的增加。然而，它们对抗CD19的同型黏附反应不同。NALM-6细胞对抗CD19表现出强烈的同型黏附反应，该反应对EDTA有抗性，且不依赖β1/β2整合素。1E8细胞仅在IL-7刺激后对抗CD19有反应；该反应对EDTA敏感，且不依赖β1/β2整合素。这些综合结果表明，IL-7不仅作为人BCP的生长因子起作用，还通过细胞表面CD19调节信号转导。
