Blumenstock F A, Saba T M, Cardarelli P M, Cho E
J Reticuloendothel Soc. 1983 Jan;33(1):21-33.
The opsonic activity of plasma fibronectin is important in modulating the reticuloendothelial system (RES) phagocytic removal of a variety of endogenous and exogenous particulate material from the vascular compartment. Purification of plasma-opsonic fibronectin by affinity chromatography with gelatin-Sepharose revealed that although in vitro hepatic Kupffer cell phagocytosis was absolutely dependent upon the presence of fibronectin, the purified fibronectin evaluated in concentrations similar to that found in plasma (350-450 micrograms/ml) supported phagocytosis at a level two- to threefold less than that observed in whole plasma. In contrast, the combination of purified fibronectin with small aliquots of opsonically inactive fibronectin-free plasma restored normal opsonic activity as assessed by liver slice bioassay and enhanced fibronectin-mediated attachment of gelatinized particulate to isolated Kupffer cells in vitro. Evidence is presented in this study that there exists in plasma a macromolecular species that amplifies the opsonic activity of fibronectin in a dose-related manner. This amplification or cofactor activity is nondialysable and has a molecular weight greater than 12,000. Inactivation of the amplification activity present in affinity-absorbed plasma can be achieved by heating the fibronectin-free plasma at 60 degrees C for 20 min, supporting the hypothesis that the cofactor is a protein. The amplification response is dose related, suggesting that the mechanism of its action is stoichiometric rather than catalytic. Evidence is presented that partial purification of the cofactor can be achieved by (NH4)2SO4 precipitation at 4 degrees C. Purification of this cofactor will provide an opportunity to evaluate its role in the altered opsonic states known to exist after trauma, burn, and sepsis.
血浆纤连蛋白的调理活性对于调节网状内皮系统（RES）从血管腔中吞噬清除各种内源性和外源性颗粒物质至关重要。用明胶 - 琼脂糖亲和层析法纯化血浆调理纤连蛋白发现，尽管体外肝库普弗细胞吞噬作用绝对依赖于纤连蛋白的存在，但以与血浆中相似的浓度（350 - 450微克/毫升）评估的纯化纤连蛋白所支持的吞噬作用水平比全血浆中观察到的低两到三倍。相反，通过肝切片生物测定评估，纯化的纤连蛋白与少量无调理活性的无纤连蛋白血浆的组合恢复了正常的调理活性，并增强了纤连蛋白介导的明胶化颗粒在体外与分离的库普弗细胞的附着。本研究提供的证据表明，血浆中存在一种大分子物质，它以剂量相关的方式放大纤连蛋白的调理活性。这种放大或辅因子活性是不可透析的，分子量大于12,000。通过将无纤连蛋白血浆在60℃加热20分钟可使亲和吸收血浆中存在的放大活性失活，这支持了辅因子是一种蛋白质的假设。放大反应与剂量相关，表明其作用机制是化学计量的而非催化的。有证据表明，通过在4℃下用硫酸铵沉淀可实现辅因子的部分纯化。纯化这种辅因子将为评估其在创伤、烧伤和败血症后已知存在的改变的调理状态中的作用提供机会。
