This document discusses various neurotrophic factors and cytokines. It describes neurotrophins like nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin 3 and 4/5 that promote nerve growth, survival and neuronal plasticity through Trk and p75 receptors. Other growth factors discussed are leukemia inhibitory factor, insulin-like growth factor, fibroblast growth factor, transforming growth factor and platelet-derived growth factor. Cytokines are small protein molecules that regulate the immune response through local and systemic effects.