Production of prostaglandin E and an interleukin-1 like factor by cultured astrocytes and C6 glioma cells.

When treated with lipopolysaccharide (LPS), cultured murine astrocytes released significant amounts of prostaglandin E, which caused an inhibition of the in vitro proliferative response of C3H/HeJ thymocytes to mitogen. In addition, an interleukin 1 (IL 1)-like factor secreted by LPS-treated glia cell cultures and by C6 glioma cells was detected. The characterization of the factor as an IL 1-like mediator is based on the findings that the factor 1) enhances the mitogen-induced thymocyte proliferation, 2) exhibits no interleukin 2 (IL 2) activity, but 3) augments IL 2 production by mitogen-stimulated thymocytes, and 4) has a m.w. between 13,500 and 18,000 when generated in serum-free conditions. These observations suggest that astrocytes may interact with the immune system by elaborating nonspecific factors that modulate lymphocyte proliferation. This property of astrocytes may be important in the generation of specific immune responses in the brain, which is considered to be an immunologically privileged organ as it is anatomically sequestered from the immune system.