The glioblastoma‐derived T‐cell suppressor factor/transforming growth factor beta2 inhibits the generation of lymphokineactivated killer (LAK) cells

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Abstract
Glioblastoma cells release factors (G‐TsF) which inhibit T‐cell proliferation. The G‐TsF is a novel member of the transforming growth factor β family and is identical to TGFβ2. The effect of G‐TsF and TGFβ2 on the induction of LAK cell activity was investigated by culturing PBL obtained from normal blood donors and brain tumour patients in varying concentrations (50–500 U/ml) of interleukin 2 (IL2) alone or IL2 plus GTsF/TGFβ2 (I ng/ml) for 4 days. Subsequent cytolytic activity was measured against autologous and allogeneic glioblastoma targets, fresh NK‐resistant melanoma cells and K562 cells. GTsF/TGFβ2 purified from glioblastoma cell cultures and TGFβ2 isolated from porcine platelets significantly suppressed the generation of LAK cell activity, and the inhibitory effect could be reduced by higher concentrations of IL2. The suppressive effect of TGFβ2 was most significant during the early stages of LAK cell generation and no inhibitory effect was seen when TGFβ2 was added directly to the cytotoxicity assay. These results suggest that human glioblastomas may exert an inhibitory influence on the generation of an immune response in vivo through the production of G‐TsF/TGFβ2, and that the inhibitory effect may be modified by IL2.

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