IL-6 EXPRESSION IN NEURONS OF TRANSGENIC MICE CAUSES REACTIVE ASTROCYTOSIS AND INCREASE IN RAMIFIED MICROGLIAL CELLS BUT NO NEURONAL DAMAGE

Growing evidence suggests that aberrant production of inflammatory cyt okines within the central nervous system (CNS) contributes to the deve lopment of pathological conditions. To test the cause-effect relations hip between the overproduction of interleukin-6 (IL-6) in the CNS and the onset of neuropathological changes, we have generated transgenic m ice in which human IL-6 expression has been targeted to the neurons by using the rat neuron-specific enolase promoter. These mice develop re active astrocytosis and an increase in ramified microglial cells but d o not show histological or behavioural signs of neuron damage at the l ight microscope level. We thus conclude that a constant release of hum an IL-6 by neuronal subpopulations in mice is sufficient to activate c ells potentially capable of modulating the local immune response, but at the same time is compatible with normal neuron functions.