Interleukin 6 (IL-6) in serum and urine of renal transplant recipients.

Hybridoma growth factor (HGF) is a 20-25 kD protein, supporting the growth of hybridoma cells in vitro and capable of replacing feeder cells. It was shown to be produced by human monocytes and a number of cultured cell lines. Recently, HGF was found to be identical to interferon-beta 2 or 26 kD protein and BSF-2, and was renamed interleukin 6 (IL-6). Using a sensitive bio-assay we were able to measure IL-6 activity in the serum and urine of healthy volunteers and renal transplant recipients. Low levels of IL-6 were present in the serum but not in the urine of healthy individuals. In contrast, both serum and urine of renal transplant recipients contained high levels of IL-6 directly after transplantation and during acute rejection episodes. On the basis of kinetic studies of the IL-6 response, it is concluded that serial measurement of IL-6, especially in urine, may be of value in monitoring renal transplant recipients. Moreover, the sensitivity of the bioassay will allow for detailed studies as to the biological significance of IL-6 in health and disease.