Masellis-Smith A, Shaw A R
Department of Immunology, University of Alberta, Canada.
J Immunol. 1994 Mar 15;152(6):2768-77.
The modulation of adhesive interaction between lymphocyte progenitors and bone marrow stroma may critically determine the maturation and migration of B cell progenitors. mAb against CD9 and beta 1 integrins are reported to induce the homotypic adhesion of pre-B cells. We present evidence that the anti-CD9 mAb 50H.19 and ALB6 but not the proaggregatory anti-VLA-4 mAb 44H6 also enhance the Fc-independent heterotypic adhesion of the human pre-B cell lines NALM-6 and HOON to bone-marrow stromal fibroblasts (BM-FB) but not to bone marrow stroma. CD9-enhanced binding of NALM-6 cells to BM-FB was inhibited 58% by the anti-VLA-4 mAb HP2/1, 36% by the anti-VLA-5 mAb BIIG2, and 99% by their combination. The mAb effectively inhibited adhesion when prebound to NALM-6 cells but not when prebound to BM-FB. The anti-VCAM-1 mAb E1/6 inhibited CD9-enhanced adhesion by only 14% suggesting the involvement of other ligands. Adhesion was inhibited by mAbs against the COOH-terminus and central cell binding domains of fibronectin, as well as by the corresponding CS1 and RGD peptides. Adhesion was not affected by H-7 and sphingosine, inhibitors of protein kinase C. These results suggest that perturbation of CD9 on pre-B cells promotes recognition of stromal cell fibronectin by VLA-4 and VLA-5 and implicates CD9 as a novel regulator of inside-out signaling relevant to B lymphopoiesis.
淋巴细胞祖细胞与骨髓基质之间黏附相互作用的调节可能对B细胞祖细胞的成熟和迁移起关键作用。据报道，抗CD9和β1整合素的单克隆抗体可诱导前B细胞的同型黏附。我们提供的证据表明，抗CD9单克隆抗体50H.19和ALB6，而非促聚集的抗VLA-4单克隆抗体44H6，也能增强人前B细胞系NALM-6和HOON与骨髓基质成纤维细胞（BM-FB）而非骨髓基质的不依赖Fc的异型黏附。抗VLA-4单克隆抗体HP2/1可使NALM-6细胞与BM-FB的CD9增强型结合受到58%的抑制，抗VLA-5单克隆抗体BIIG2可使其受到36%的抑制，二者联合使用则可使其受到99%的抑制。这些单克隆抗体预先结合到NALM-6细胞上时能有效抑制黏附，而预先结合到BM-FB上时则不能。抗VCAM-1单克隆抗体E1/6仅使CD9增强型黏附受到14%的抑制，这表明还有其他配体参与其中。抗纤连蛋白COOH末端和中央细胞结合结构域的单克隆抗体以及相应的CS1和RGD肽均可抑制黏附。蛋白激酶C的抑制剂H-7和鞘氨醇对黏附没有影响。这些结果表明，前B细胞上CD9的扰动促进了VLA-4和VLA-5对基质细胞纤连蛋白的识别，并表明CD9是与B淋巴细胞生成相关的一种新型外向内信号调节因子。
