Involvement of IL-6 in mesangial proliferative glomerulonephritis.

In this study, we demonstrated that IL-6 was a possible autocrine growth factor for rat mesangial cells (MC). rIL-6 induced in vitro growth of rat MC at a concentration of 2 to 200 ng/ml and IL-6 activity was found in the supernatant of cultured rat MC. Northern blot analysis as well as in situ hybridization revealed that IL-6 mRNA was expressed in the cultured MC. Of urine samples from patients with mesangial proliferative glomerulonephritis (PGN) 50% were found to contain significant IL-6 activity (ranging from 30 to 126 pg/ml). Urine samples from other type of primary glomerular diseases such as minimal change nephrotic syndrome or healthy volunteers contained no detectable IL-6 activity. Only 2 of 27 urine samples from membranous nephropathy contained detectable amount of IL-6. Furthermore, there was some relationship between the levels of urine IL-6 and the progressive stage of PGN. Finally, by immunohistochemical staining using an anti-IL-6 mAb, it was shown that MC in the affected glomeruli of PGN patients produced IL-6, whereas MC obtained from the patients with membranous nephropathy, minimal change nephrotic syndrome or normal kidney were not found to produce IL-6. These data suggest that deregulated production of IL-6 is involved in PGN and the measurement of urine IL-6 is helpful for the differential diagnosis of PGN as well as for monitoring the progression of PGN.