Differential oligodendroglial expression of the tumor necrosis factor receptors in vivo and in vitro.

The cytokine tumor necrosis factor-alpha (TNF alpha) has been proposed to play a key role in the degenerative processes observed in demyelinating diseases such as multiple sclerosis (MS). In the immune system the cellular responses to TNF are mediated by two different receptors: TNF-RI, which is involved in cell death, and TNF-RII, which has been shown to mediate cell proliferation. We investigated the oligodendroglial expression of TNF-RI and -RII. In vivo, in normal adult rodent brain, oligodendrocytes express TNF-RII but not TNF-RI. However, after 3 days in culture, both types of receptors were expressed by mature oligodendrocytes, purified from 4-week-old rats, suggesting that expression of TNF-RI was induced by either the isolation process or the culture conditions. This inducibility of TNF-RI may explain the differences in oligodendrocyte cell death reported in various experimental conditions and in the pathology of MS lesions.