Arachidonic acid in the reticuloendothelial network.

Introduction The role of fatty acids in the reticuloendothelial system has been studied in a variety of ways, including dietary modification of tissue [ 1-41, analysis of the effects of exogenous fatty acids in vitro [S-91 and investigation of the enzymes of fatty acid metabolism [ 10191. These approaches have indicated a unique and selective role for arachidonic acid in cell signalling in the immune system. In some pathways, such as Fc y-mediated superoxide generation [S] and in tumour necrosis factor (TNF)-induced cytotoxicity [lo], arachidonic acid appears to be an obligatory mediator. In other pathways such as lipopolysaccharide priming, the release of arachidonic acid may facilitate the responses to other stimuli [7,11,15,16,20]. Recently, attempts have been made to quantify the flux of metabolites through arachidonateassociated pathways [14,21]. In this paper it will be proposed that these approaches can be integrated into network analysis of the immune system. These second-generation immune networks can incorporate the arachidonate-mediated intracellular and intercellular events that dynamically connect individual elements of the reticuloendothelial system [22-251. The advantage of network analysis is that it is possible to investigate the patterns of co-operative responses that define emergent properties. Such properties include the development of immunological memory [22-241.