Sheth B, Dransfield I, Partridge L J, Barker M D, Burton D R
Department of Biochemistry, University of Sheffield, U.K.
Immunology. 1988 Mar;63(3):483-90.
Treatment of the U937 cell line with 1 mM dibutyryl cyclic AMP (Bt2cAMP) resulted in a reduction in cell size and inhibition of DNA synthesis, and morphologically the cells appeared similar to macrophages. Electron micrographs indicated an increase in intracellular apparatus, whilst histochemical studies revealed smaller, denser nuclei and a greater intensity of non-specific esterase staining. Ia-like antigens (HLA-DR and HLA-DC) and complement receptor CR1 were not detected on U937 cells by monoclonal antibodies, nor were they induced by Bt2cAMP. CR3 was present in small amounts on U937 cells, and stimulation with Bt2cAMP increased the expression of this molecule in the cytoplasm and on the cell surface. Leu M3, a monocyte-specific antibody, was weakly reactive on both unstimulated and stimulated cells, whereas transferrin receptors, present on 90% of U937 cells, were lost after 48-hr stimulation with Bt2cAMP. JW6 and NH6, two monoclonal antibodies raised in our laboratory and found to be against immature monocytic antigens, showed decreased expression on stimulation. Monomer IgG binding via Fc receptors decreased on stimulated cells, and a monoclonal antibody (32.2) specific for FcRI confirmed this to be due to a decrease in the number of high-affinity receptors, rather than a decrease in IgG-binding affinity. In contrast, expression of the low-affinity FcRII, monitored by monoclonal antibody IV3, increased dramatically after stimulation. Other functional changes included the production of superoxide anions and the induction of non-specific phagocytosis. Two dimensional gel analysis, of detergent soluble proteins from unstimulated and 48-hr stimulated U937 cells, showed many differences in protein expression. A detailed investigation of these changes will facilitate a better understanding of the molecular mechanisms involved in the differentiation of U937 cells.
用1 mM二丁酰环磷腺苷（Bt2cAMP）处理U937细胞系会导致细胞大小减小和DNA合成受到抑制，并且在形态上这些细胞看起来类似于巨噬细胞。电子显微镜照片显示细胞内细胞器增加，而组织化学研究揭示细胞核更小、更致密，非特异性酯酶染色强度更高。单克隆抗体未在U937细胞上检测到Ia样抗原（HLA-DR和HLA-DC）和补体受体CR1，Bt2cAMP也未诱导它们的产生。CR3在U937细胞上少量存在，用Bt2cAMP刺激会增加该分子在细胞质和细胞表面的表达。单核细胞特异性抗体Leu M3在未刺激和刺激的细胞上均呈弱反应性，而90%的U937细胞上存在的转铁蛋白受体在用Bt2cAMP刺激48小时后消失。在我们实验室产生的、发现针对未成熟单核细胞抗原的两种单克隆抗体JW6和NH6在刺激后表达降低。通过Fc受体结合的单体IgG在刺激细胞上减少，一种针对FcRI的单克隆抗体（32.2）证实这是由于高亲和力受体数量减少，而不是IgG结合亲和力降低。相反，用单克隆抗体IV3监测的低亲和力FcRII的表达在刺激后显著增加。其他功能变化包括超氧阴离子的产生和非特异性吞噬作用的诱导。对未刺激和用Bt2cAMP刺激48小时的U937细胞的去污剂可溶性蛋白质进行的二维凝胶分析显示蛋白质表达存在许多差异。对这些变化的详细研究将有助于更好地理解U937细胞分化所涉及的分子机制。
