Cytokines

Abstract

Cytokines encompass diverse groups of multifunctional proteins that play key roles in a variety of biological processes, including cell growth and activation, inflammation, immunity, hematopoiesis, tumorigenesis, tissue repair, fibrosis, and morpho-genesis. Chemotaxis is stimulated by a recently defined group of cytokines, the chemokines. Consistent with their relatively diverse functions, cytokines are synthesized in a variety of cell types, including cells of the mononuclear phagocyte system, lymphocytes, epithelial cells, fibroblasts, endothelial cells, and chondrocytes. These peptides interact with receptors on a wide variety of cell types to initiate intracellular signaling cascades that are responsible for mediating their effects. Interactions of the cytokines with these receptors can occur locally in an autocrine fashion on the cells that produced the cytokine or in a paracrine fashion on cells adjacent to the site of production. Finally, cytokines can function at distant sites in an endocrine fashion. This chapter will provide an overview of the major cytokines and their actions, their receptors and intracellular signaling cascades, and the role of cytokines and their receptors in specific disease processes.