Transgenic Mice Expressing Cytokines in the CNS as Model Systems for the Study of Inflammatory Neurodegenerative and Demyelinating Disorders

Cytokines are a diverse group of small molecular weight, soluble factors that were originally discovered as products of activated immune cells and which play a central role in immune regulation.1,2 However, it is now clear that these multifunctional factors are produced by and act on not only immune cells but virtually all cell types examined. Like hormones, cytokines exert their actions by binding to specific receptors on the surface of cells activating intracellular signaling pathways that result in the modulation of gene transcription. Unlike hormones which are largely endocrine regulators, cytokines tend to act in a more localized milieu influencing the function of immediately neighboring cells (termed paracrine regulation) or the producer cells themselves (termed autocrine regulation). In vivo, cytokines exert their actions within the context of a highly complex and yet tightly regulated network in which the cellular response evoked represents the sum of the overlapping, synergistic and antagonistic actions of multiple cytokines.