INTERLEUKIN-8 AND MONOCYTE CHEMOTACTIC PROTEIN-1 PRODUCTION BY A HUMAN GLIOBLASTOMA CELL-LINE, T98G IN COCULTURE WITH MONOCYTES - INVOLVEMENT OF MONOCYTE-DERIVED INTERLEUKIN-1ALPHA

We have previously demonstrated that a human glioblastoma cell line, T 98G cells, produced high levels of interleukin-8 (IL-8) and monocyte c hemotactic protein-1 (MCP-1) when stimulated with IL-1 or tumor necros is factor-alpha (TNF-alpha). In this study, we found that T98G cells a re capable of producing large amounts of IL-8 and MCP-1 when coculture d with human peripheral blood monocytes or a monocytic cell line, U937 cells. Since it is possible that both glioblastoma cells and monocyte s are capable of producing chemokines, we determined which type of cel ls actually produced IL-8 and MCP-1, by the fixation of one or the oth er cell type with 3% paraformaldehyde (PA). This procedure revealed th at T98G cells were the main source and that PA-treated monocytes effec tively stimulated IL-8 and MCP-1 production by T98G cells. Both IL-8 a nd MCP-1 gene expression and protein production by T98G cells were con firmed by northern blot as well as immunohistochemical staining method s. To analyze the molecules on human monocytes responsible for inducin g IL-8 and MCP-1 by T98G cells, several antibodies (Abs) as well as IL -1 receptor antagonist (IL-1Ra) were tested, Anti-IL-1 alpha Ab and IL -1Ra almost completely abolished the IL-8/MCP-1-inducing capacity of t he PA-fixed monocytes, while no inhibition was obtained with anti-IL-1 beta, anti-TNF-alpha or Abs against CD11b/18, L-selectin or ICAM-1, i ndicating that membrane-associated IL-1 alpha is involved in the IL-8/ MCP-1 induction, while secreted IL-1 alpha plays a major role in this cell-to-cell, i.e., juxtacrine interaction in unfixed conditions.