Study on Early Process of B Cell Differentiation

实验血液学现在有一个生长因子清单，其中包含近20个不同的分子作用于不同血细胞系的细胞。尽管列出尽可能多的造血生长因子是很重要的，但随着参与造血系统的分子数量的增加，获得完整的造血系统的清晰图像变得更加困难。这个国际合作项目的主要目的是为建立一个简化的造血系统模型铺平道路。在这个项目的过程中，两个生长因子/受体系统被证明构成了造血系统的核心结构。一种是c-FMS/M-CSF系统，另一种是c-kit/SCF系统。首先，我们与Jackson实验室的L.D.Schultz博士合作，证明了一种突变，即骨化症(OP)，它是在M-CSF编码区插入单个核苷酸，从而使M-CSF的生物学活性被取消。进一步的组织学检查IND…进一步证明，在没有M-CF的情况下，巨噬细胞的生成是维持的。另一方面，破骨细胞的生成完全依赖于M-CSF，而破骨细胞的生成是制备骨腔所必需的。C-FMS/M-CSF系统可能是维持骨髓内造血的重要系统，但即使在有骨腔的情况下，如果缺乏支持干细胞自我更新的系统，也不能维持骨髓内的造血。由于先前对c-kit或其配体功能缺陷的突变小鼠的表型分析表明，该系统可能构成造血干细胞自我更新的核心结构。为了测试这种可能性，我们建立了分泌抗c-kit单克隆抗体的杂交瘤。利用其中一种能阻断c-kit功能的单抗，我们研究了c-kit/SCF系统在骨髓内造血中的作用。我们的结果表明，髓系和红系干细胞的自我更新绝对需要c-kit/SCF。与阿拉巴马大学的马克斯·库珀博士、弗里茨·梅尔切斯博士以及巴塞尔免疫研究所的罗纳德·帕拉西奥斯、弗里茨·梅尔彻和安东尼乌斯·罗林克博士合作，我们还证明了c-kit在早期淋巴细胞前体细胞系的表面表达。综上所述，c-kit/SCF系统构成了包括淋巴干细胞在内的各种造血干细胞自我更新的核心分子结构，由此我们提出了一种简化的模型，即受体类型酪氨酸激酶及其配体构成骨髓内造血的核心结构，其他细胞因子受体家族分子及其配体围绕该核心结构，可能在保证造血系统的灵活性方面发挥作用。通过研究造血系统的系统发育和个体发育，这一模型很可能是可检验的，这方面的研究目前正在我们实验室进行。较少

Experimental hematology has now a list of growth factors, which contains nearly 20 distinct molecules acting on the cells of various blood cell lineages. Although it is important to list as many hematopoietc growth factors as possible, however, it become more difficult to have a clear image of hematopoietic system in toto as the number of molecules involved in the system increases. The major purpose of this international collaboratory project is pave a way towards a simplified model of hematopoietic system.During the course of this project, two growth factor/receptor systems have been demonstrated to constitute the core structure of hematopoietic system. One is c-fms/M-CSF system, and the other is c-kit/SCF system.First, in collaboration with Dr. L. D. Schultz in Jackson Laboratory, we have demonstrated that a mutation, osteopetrosis(op), is a single nucleotide insertion within M-CSF coding region, by which biological activity of M-CSF is abrogated. Further histological examination ind … More icated that macrophage generation is maintained in the absence of M-CF. On the other hand, osteoclast generation whuch is indispensable for preparing bone cavity, is absolutely dependent on M-CSF. Noting a simple fact that there is no intramarrow hematopoiesis without bone cavity, c-fms/M-CSF system may well be a essential system for maintaining the intramarrow hematopoiesis.Even in the presence of bone cavity, however, no intramarrow hematopoiesis is maintained if the system supporting self-renewal of stem cell is absent. Since Previous phenotype analysis of mutant mice defective in the functions of c-kit or its ligand suggested that this system could constitute the core tructue for hematopoietic stem cell self-renewal. To test this possibility, we have estabished hybridomas which secrete anti-c-kit moneclonal antibody. Using one of these mAb which can block c-kit function, we investigated the role of c-kit/SCF system in intramarrow hematopoiesis. Our result indicated that the self-renewal of myeloid and erythroid stem cells requires c-kit/SCF absolutely. In collaboration with Dr. Max Cooper in Alabama Univ., Frirtz Melchers, and Drs. Ronald Palacios, Fritz Melchers, and Antonius Rolink in Basel Institute for Immunology, we also demonstrated that c-kit isexpressed on the surface of early lymphocyte Precursors cell lines. Taken together, it is clear that c-kit/SCF system constitutes a core molecular structure for the self-renewal of all kinds of hematopoietic stem cells including lymphoid stem cells.From these results, we are proposing a simplified model that receptor type tyrosine kinases and their ligands form a core structure of intramarrow hematopoiesis, and other cytokine receptor family molecules and their ligands are placed around this core structure, Probably Playing a role for ensuring the flexibility of hematopoietic system. This model might well be testable by investigating phylogenical and ontogenical development of hematopoietic system, and the investigation along this line is currently carried out in our laboratory. Less