Purification and Characterization of Soluble Human IL-6 Receptor Expressed in CHO Cells

An immunosorbent assay system to detect genetically engineered IL-6 receptor (IL-6R) was established, whereby soluble IL-6 receptor (sIL-6R) was detected in the culture medium when sIL-6R cDNA was transfected into COS1 cells. A stably transformed Chinese hamster ovary (CHO) cell line constitutively expressing sIL-6R has been established. The recombinant sIL-6R was purified to homogeneity by sequential filtration and chromatography of the culture medium. The recombinant sIL-6R augmented the sensitivity of M1 cells to IL-6 in growth inhibition assay in a dose-dependent manner. Furthermore, a radioisotope immunosorbent assay (RIA) utilizing recombinant sIL-6R was established which could detect IL-6 in a quantity as low as 10 ng/ml.