Jacobsen K, Miyake K, Kincade P W, Osmond D G
Department of Anatomy, McGill University, Montreal, Canada.
J Exp Med. 1992 Oct 1;176(4):927-35. doi: 10.1084/jem.176.4.927.
B lymphocyte precursor cells in mouse bone marrow develop in close association with stromal cells which provide essential growth signals. To identify molecules that may normally play a role in this interaction we have examined the in vivo binding of a new monoclonal antibody (mAb) (KMI6) that recognizes a determinant on a bone marrow stromal cell line (BMS2) in vitro. Flow cytometric and radioautographic evaluations revealed that the antigen recognized by KMI6 is represented on the surface of an extremely small number of cells in bone marrow cell suspensions from adult mice. An apparent molecular mass of 110 kD was obtained by surface labeling of a stromal cell clone and immunoprecipitation. Purified mAb KMI6 labeled with 125I was then given intravenously to young C3H/HeJ mice. Unbound mAb was washed out by cardiac perfusion and femoral bone marrow was examined by light and electron microscope radioautography. KMI6 labeling was heavy on the plasma membrane of many stromal cells, especially those located towards the outer subosteal region. The KMI6-labeled stromal cells were usually associated with cells of lymphoid morphology which they often completely surrounded. The labeling was restricted to areas of stromal cell plasma membranes in contact with lymphoid cells. The lymphoid cells themselves, as well as macrophages and other hemopoietic cells, failed to bind mAb KMI6 significantly. Stromal cells in bone marrow depleted of hemopoietic cells by gamma-irradiation (9,5 Gy) bound mAb KMI6 at reduced intensity. The results demonstrate that the KMI6 determinant, a 110-kD protein, is expressed on bone marrow stromal cells in vivo. Its restriction to areas of interaction with lymphoid cells suggests a role in forming microenvironmental niches of B lymphopoiesis. The surface membrane of individual stromal cells may thus be functionally polarized towards interacting B cell precursors and other hemopoietic cells.
小鼠骨髓中的B淋巴细胞前体细胞与提供重要生长信号的基质细胞紧密相连而发育。为了鉴定可能在这种相互作用中正常发挥作用的分子，我们检测了一种新的单克隆抗体（mAb）（KMI6）在体内的结合情况，该抗体在体外可识别骨髓基质细胞系（BMS2）上的一个决定簇。流式细胞术和放射自显影评估显示，KMI6识别的抗原在成年小鼠骨髓细胞悬液中极少数细胞的表面表达。通过对一个基质细胞克隆进行表面标记和免疫沉淀，得到了一个表观分子量为110 kD的蛋白。然后将用125I标记的纯化mAb KMI6静脉注射给年轻的C3H/HeJ小鼠。通过心脏灌注洗去未结合的mAb，并通过光学显微镜和电子显微镜放射自显影检查股骨骨髓。KMI6标记在许多基质细胞的质膜上很重，尤其是那些位于骨膜下外层区域的细胞。KMI6标记的基质细胞通常与具有淋巴样形态的细胞相关联，它们常常将这些细胞完全包围。标记仅限于基质细胞质膜与淋巴细胞接触的区域。淋巴细胞本身以及巨噬细胞和其他造血细胞未能显著结合mAb KMI6。经γ射线照射（9.5 Gy）使造血细胞耗竭的骨髓中的基质细胞与mAb KMI6的结合强度降低。结果表明，KMI6决定簇，一种110-kD蛋白，在体内骨髓基质细胞上表达。其在与淋巴细胞相互作用区域的局限性表明它在形成B淋巴细胞生成的微环境龛中起作用。因此，单个基质细胞的表面膜在功能上可能向相互作用的B细胞前体和其他造血细胞极化。
