Prostaglandin E2 as an immunomodulating factor released in vitro by human glioma cells

Cultured human glioma cells were found to produce soluble factors that can modulate the in vitro proliferative response of purified T lymphocytes stimulated by phytohemagglutinin (PHA). Neoplastic tissue was removed during surgery for brain glial tumors and cultured in vitro. The glial nature of the neoplastic cells was verified by means of anti-glial fibrillary acidic protein immunohistochemical staining. Serum-free supernatants from these cultures proved capable of suppressing in vitro proliferation of PHA-stimulated T lymphocytes. Suppression was reduced when indomethacin or aspirin was added to the culture medium. Thin-layer chromatography revealed the presence of prostaglandins and other arachidonic acid derivatives in the supernatants. The radioimmunoassay used to quantify the prostaglandin E2 (PGE2) in the supernatants showed detectable amounts of PGE2, which disappeared after the cultures had been treated with anti-inflammatory drugs. These data support the hypothesis that tumoral glial cells can play a role in the host immune response in the central nervous system, namely by producing soluble factors.