Ghebrehiwet B, Kew R R, Gruber B L, Marchese M J, Peerschke E I, Reid K B
Department of Medicine, State University of New York, Stony Brook 11794, USA.
J Immunol. 1995 Sep 1;155(5):2614-9.
Although previous studies have shown that different cells and cell lines of murine origin bind human C1q, suggesting that they display cell surface receptors for C1q, no information is available to indicate whether mouse or human mast cells express C1q receptors. This paper presents the first evidence to show that murine mast cells express specific receptors for C1q. Western blot analysis of cell membrane proteins prepared from a bone marrow-derived mouse cell line using two monospecific polyclonal Abs, one directed against the 60-kDa C1q receptor (C1q-R) that binds to the collagen-like stalk of C1q (cC1q-R) and the other directed against the 33-kDa molecule that binds to the globular "heads" of C1q (gC1q-R), show that both of these receptors are present on these cells. In addition, C1q can induce mast cell migration in a specific and dose-dependent manner. Interestingly, the C1q-induced migratory response was found to be biphasic; the first response peaked at a C1q concentration of 0.1 nM, whereas the second phase peaked at approximately 40 nM. Checkerboard analysis of the mast cell migratory response to C1q showed that the first phase was primarily due to chemotaxis and the second phase was attributable to chemokinesis. Preincubation of C1q with Abs specific for the collagen-like tail of the molecule abolished both its chemotactic and chemokinetic response, whereas heat inactivation of C1q (56 degrees C, 1 h) resulted in 85% abrogation of the chemotactic phase and 42% reduction in the chemokinetic phase. The observed mast cell migratory responses were mediated by cell surface C1q-R(s), as inclusion of a mixture of anti-C1q-R and anti-gC1q-R Abs with the cells inhibited their migratory response toward C1q. However, incubation of cells with various doses of C1q did not result in histamine release. Furthermore, engagement of mast cell C1q-Rs by the ligand C1q induced an antiproliferative response, as coculturing of mast cells with C1q resulted in a specific and dose-dependent decrease in DNA synthesis. These data suggest that C1q-Rs may play a significant role in mast cell function and regulation by providing an important signal through which mast cells can be recruited to inflammatory sites of increased C1q concentration.
尽管先前的研究表明，源自小鼠的不同细胞和细胞系可结合人C1q，提示它们表达C1q的细胞表面受体，但尚无信息表明小鼠或人肥大细胞是否表达C1q受体。本文首次提供证据表明小鼠肥大细胞表达C1q的特异性受体。使用两种单特异性多克隆抗体对源自骨髓的小鼠细胞系制备的细胞膜蛋白进行蛋白质印迹分析，一种抗体针对与C1q的胶原样柄结合的60 kDa C1q受体（C1q-R），另一种针对与C1q的球状“头部”结合的33 kDa分子（gC1q-R），结果表明这两种受体均存在于这些细胞上。此外，C1q能够以特异性和剂量依赖性方式诱导肥大细胞迁移。有趣的是，发现C1q诱导的迁移反应呈双相性；第一个反应在C1q浓度为0.1 nM时达到峰值，而第二阶段在约40 nM时达到峰值。对肥大细胞对C1q迁移反应的棋盘分析表明，第一阶段主要归因于趋化作用，第二阶段归因于趋动作用。用针对该分子胶原样尾部的特异性抗体对C1q进行预孵育，可消除其趋化和趋动反应，而C1q热灭活（56℃，1小时）导致趋化阶段减少85%，趋动阶段减少42%。观察到的肥大细胞迁移反应由细胞表面的C1q-R介导，因为将抗C1q-R和抗gC1q-R抗体混合物与细胞一起孵育会抑制它们对Cq的迁移反应。然而，用不同剂量的C1q孵育细胞并未导致组胺释放。此外，配体C1q与肥大细胞C1q-R的结合诱导了抗增殖反应，因为肥大细胞与C1q共培养导致DNA合成特异性和剂量依赖性降低。这些数据表明，C1q-R可能通过提供一个重要信号在肥大细胞功能和调节中发挥重要作用，通过该信号肥大细胞可被募集到C1q浓度升高的炎症部位。
