Analysis of tumor necrosis factor and lymphotoxin secreted by incubation of lymphokine-activated killer cells with tumor cells

Inhibition of tumor necrosis factor-alpha and -beta secretion by lymphokine activated killer cells by transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) has a variety of immunosuppressive properties. We investigated the effect of TGF-beta secreted by glioblastoma (T98G) cells on the secretion of tumor necrosis factor-alpha and -beta (TNFs) by lymphokine activated killer (LAK) cells stimulated with tumor cells. The supernatant from T98G cells was preincubated with anti-TGF-beta 1 and -beta 2 neutralizing antibodies or untreated, and added to a coculture of LAK and Daudi cells. The neutralizing antibodies were added to LAK/Daudi and LAK culture, and natural human TGF-beta 1 and recombinant human TGF-beta 2 were also added to the LAK/Daudi culture. LAK cells were also cultured with T98G cells, of which the supernatant contained both active and latent forms of TGF-beta 1 and TGF-beta 2, and the neutralizing antibodies were added to the coculture. TNFs activity in the supernatants from LAK/Daudi cultures was examined by a specific bioassay. Addition of the supernatant from T98G cells to LAK/Daudi culture resulted in the inhibition of TNFs secretion by LAK cells. The inhibition was abrogated by the pretreatment of the supernatants with the anti-TGF-beta antibodies. Addition of TGF-beta 1 and TGF-beta 2 to LAK/Daudi culture inhibited TNFs secretion by LAK cells in a dose-dependent manner. Addition of anti-TGF-beta antibodies to LAK culture resulted in an increase of TNFs secretion. These results suggest that, if tumor cells have the capacity to convert TGF-beta from a latent to an active form, the active TGF-beta suppresses TNFs secretion by LAK cells stimulated with the tumor cells, and that TGF-beta secreted and activated by glioblastoma cells suppresses the propagation of immune reaction by inhibiting TNFs secretion by activated lymphocytes adjacent to tumor cells.

Antiproliferative cytokines secreted by lymphokine-activated killer cells stimulated with tumor cells

Antiproliferative cytokine secretion by lymphokine-activated killer (LAK) cells during coculture with glioblastoma cell lines, autologous glioma cells, and nongliomatous tumor cell lines (Daudi and K562 cells) was assessed, as was the antiproliferative activity of the culture supernatants against the T98G (glioblastoma) cell line. A neutralization test using agents against interferon-gamma (IFN-gamma), tumor necrosis factor (TNF), and lymphotoxin (LT) showed that antiproliferative activity was due to IFN-gamma, but not to TNF or LT. Nongliomatous tumor cells stimulated LAK cells to secrete cytokines, but gliomatous tumor cells did not. It was found that there is a discrepancy between the LAK cell capability to lyse malignant glioma cells and the ability to secrete cytokines. This may be due to the factors secreted by glioblastoma cells.