van den Dobbelsteen M E, van der Woude F J, Schroeijers W E, van Es L A, Daha M R
Department of Nephrology, University Hospital Leiden, The Netherlands.
Kidney Int. 1993 Mar;43(3):544-53. doi: 10.1038/ki.1993.81.
Primary rat mesangial cells (MC) were cultured in RPMI-1640 containing 5% fetal calf serum (FCS). The cells produced interleukin-6 (IL-6) in vitro depending on the concentration of FCS in the medium. Binding of soluble aggregates of IgG (AIgG) to MC was visualized with AIgG coupled with aminomethyl coumarin acetic acid (AMCA). There was a dose-dependent binding of 125I-AIgG to MC at 4 degrees C. Scatchard analysis revealed binding of AIgG containing 20 to 24 molecules per aggregate, with an affinity of 2.2 x 10(8) M-1 and a total average number of 2.7 x 10(5) sites per cell. The binding of AIgG or immune complexes to MC resulted in enhanced production of IL-6 by MC in culture. This enhanced production of IL-6 was dependent on the concentration of AIgG. To our surprise, preparations of monomeric IgG (mIgG) also enhanced the production of IL-6 by MC, but to a lower extent when compared to levels induced by AIgG. Very little amounts of aggregated F(ab')2 fragments [AF(ab')2] bound to MC and consequently no significant enhancement of IL-6 release by AF(ab')2 was seen, suggesting that IL-6 production is an Fc receptor-mediated phenomenon. The production of IL-6 by MC is inhibitable by cycloheximide, thus indicating de novo synthesis. Northern blot analysis revealed a threefold increase in mRNA for IL-6 by AIgG in vitro. The increase in mRNA expression was directly related to the quantity of IL-6 released in the supernatant by MC. These results suggest that binding of AIgG or immune complexes to MC in vivo may induce IL-6 production by MC, thus leading to proliferation of MC.
原代大鼠系膜细胞（MC）在含有5%胎牛血清（FCS）的RPMI - 1640培养基中培养。细胞在体外产生白细胞介素 - 6（IL - 6），这取决于培养基中FCS的浓度。用与氨甲基香豆素乙酸（AMCA）偶联的IgG可溶性聚集体（AIgG）来观察其与MC的结合情况。在4℃时，125I - AIgG与MC的结合呈剂量依赖性。Scatchard分析显示，每个聚集体含有20至24个分子的AIgG具有结合作用，其亲和力为2.2×10(8) M-1，每个细胞的总平均结合位点数量为2.7×10(5) 个。AIgG或免疫复合物与MC的结合导致培养中的MC产生IL - 6增加。IL - 6的这种增加的产生取决于AIgG的浓度。令我们惊讶的是，单体IgG（mIgG）制剂也能增强MC产生IL - 6，但与AIgG诱导的水平相比程度较低。极少量的聚集F(ab')2片段[AF(ab')2]与MC结合，因此未观察到AF(ab')2对IL - 6释放有显著增强作用，这表明IL - 6的产生是一种Fc受体介导的现象。MC产生IL - 6可被环己酰亚胺抑制，因此表明是从头合成。Northern印迹分析显示，体外AIgG可使IL - 6的mRNA增加三倍。mRNA表达的增加与MC在上清液中释放的IL - 6量直接相关。这些结果表明，体内AIgG或免疫复合物与MC的结合可能诱导MC产生IL - 6，从而导致MC增殖。
