Cytokines and neurotrophins interact in normal and diseased states.

Neurotrophins (NTs) such as nerve growth factor (NGF) as well as cytokines, for example, interleukin-6 (IL-6), are communicators between the nervous and immune systems. There is evidence for mutual interactions between NTs and cytokines. Strategies are being developed to elucidate the molecular mechanism/s of interactions and to understand how cytokines are involved in health and disease. Analysis of underlying signaling pathways in glial cells indicates that different transcription factors, such as NF-kappa B, cAMP-responsive-element binding protein (CREB), and activator protein 1 (AP-1), are involved in NT induction. IL-6 and NTs of the NGF family are coexpressed at sites of nerve injury. Interactions of these factors could modulate both neuronal de- and regeneration: IL-6 in conjunction with its soluble IL-6 receptor induces a specific pattern of NTs in astrocytes in defined brain regions. This indicates that the IL-6 system mediates a local supply of NTs that participate in diverse CNS functions, such as protection of neurons from insults, neuronal survival, and neuroimmune responses.