[Cytokine network involved in inflammatory reactions].

A cytokine, present in a minute amount in vivo, generally exhibits multiple functions shared by other cytokines. The recent progress in molecular biology and protein chemistry have facilitated identification of the structures and functions of cytokines and their receptors. This has resulted to the clinical application of several cytokines, such as granulocyte colony-stimulating factor and erythropoietin. However, the elucidation of the pathophysiological roles of cytokines in various diseases, has been hindered by a complicated network where cytokines regulate the production and/or functions of others. The utilization of homologous recombination and ES cells has led to the generation of mice that are deficient in a particular cytokine or cytokine receptor gene. Analyses of these deficient mice have given us invaluable information to unravel the roles of each cytokine or cytokine receptor. Here, we described our studies on the pathophysiological roles of pro-inflammatory cytokines using cytokine or cytokine receptor gene-deficient mice to provide examples of the usefulness of these mice in clarifying the cytokine network.