Expression of interleukin-6 gene in human astrocyte cell lineages

Expression of the lymphokine genes in human astroglial cell lineages was studied. Primers for 7 different human lymphokines, from interleukin-1a (IL-1a) to interleukin-6 (IL-6), were used to analyze RNA transcripts in 5 cultured human astrocytoma cell lines and 9 brain specimens by polymerase chain reaction (PCR). Two out of 5 unstimulated astrocytomas, U138MG and U373MG, expressed IL-6 genes. After stimulation with IL1beta, all astrocytoma and one neuroblastoma cell lines expressed IL-6 genes, but other leukemic cell lines did not show RNA transcripts of IL-6. In addition to the cultured cells, we examined IL-6 gene expression within human malignant astrocytoma, peritumoural brain and autopsied normal brains. The result shows that tumour and cells of the surrounding reactive lesion express IL-6 genes, but it is not expressed in normal brains. Next, the concentration of IL-6 in the supernatant of cultured cells was measured quantitatively by sandwich immunoassay, ELISA. IL-6 activity was present, but low in all astrocytomas with the exception of A172. Furthermore, the concentration of IL-6 increased markedly with the stimulation of IL-1beta in both a time- and dose-dependent fashion. A172 could also produce IL-6 as was seen in gene expression. From these results, it is suspected that astroglial cell-derived IL-6 may participate in local immune reactions accompanying infection, degeneration and malignancies in the central nervous system.