Cytokine signals propagate through the brain

Interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) are proinf lammatory cytokines that are constitutively expressed in healthy, adult bra in where they mediate normal neural functions such as sleep. They are neuro modulators expressed by and acting on neurons and glia, IL-1 and TNF alpha expression is upregulated in several important diseases/disorders, Upregula tion of IL-1 and/or TNF alpha expression, elicited centrally or systemicall y, propagates through brain parenchyma following specific spatio-temporal p atterns. We propose that cytokine signals propagate along neuronal projecti ons and extracellular diffusion pathways by molecular cascades that need to be further elucidated, This elucidation is a prerequisite for better under standing of reciprocal interactions between nervous, endocrine and immune s ystems.