Leukaemia inhibitory factor mRNA is expressed in the brains of patients with subacute sclerosing panencephalitis

We have examined the in situ transcription of leukaemia inhibitory factor (LIF) in brain tissue from 3 cases of subacute sclerosing panencephalitis (SSPE) and in 2 non-neurological control brains. This has been compared with expression of interleukin 2 (IL-2), interleukin 6 (IL-6) and tumour necrosis factor beta (TNF beta) in the same tissues. All of the cytokines in the study were expressed in cells in the inflammatory infiltrate as well as in glial cells. LIF mRNA was also found to be expressed in neurons, in foci where these cells were also virally infected. No hybridization was found with any of the probes in areas of SSPE brain, which were negative for measles virus RNA or in the non-neurological control cases, although expression was demonstrated in the latter by use of reverse transcription-polymerase chain reaction (RT-PCR). Differentiated, cultured human neuronal cells were also positive, by RT-PCR, for LIF. This is the first demonstration of LIF expression in human brain and the results suggest that this cytokine is up-regulated, in several cell types, including neurons, following virus infection.