Constitutive expression of interleukin-1β (IL-1β) in rat oligodendrocytes

The RT-PCR analysis of RNA from progenitor and differentiated primary rat oligodendrocytes, and from the oligodendrocyte CG-4 cell line, shows the presence of the IL-1β mRNA, the type I IL-1 receptor and the IL-1 receptor accessory protein in these cells. In situ hybridization of a rat IL-1β probe to primary progenitor and differentiated rat oligodendrocytes results in a positive signal. The double hybridization of the IL-1β probe, together with an oligodendrocyte-specific differentiation marker, to sections of postnatal rat brain at different stages of differentiation is also positive. The double immune-labelling technique utilized indicates coincidence of the signals on the brain slices. The results show that IL-1β mRNA is constitutively expressed in rat brain oligodendrocytes from 1 day after birth onward. In agreement with this observation, CG-4 cells, primary progenitor and differentiated rat oligodendrocytes are positively stained by antibodies against IL-1β. Postnatal brain slices from 1 and 4 day old and adult rats, labelled with a double immunofluorescence technique, are also stained by antibodies against IL-1β. This signal coincides with that of antibodies against oligodendrocyte-specific surface markers. We conclude that IL-1β is constitutively expressed in rat brain progenitor and differentiated oligodendrocytes.