Controlling the immune system: diffuse feedback via a diffuse informational network.

Diffuse feedback is defined to be a process by which a system in some sense improves its performance with respect to a variety of conflicting and even contradictory goals. In the immune system, such feedback is mediated by scores of extracellular chemicals (cytokines), each of which participates in achieving several goals. Progress toward any given goal is mediated by several cytokines. The 'immunoinformatics' of this diffuse informational network will be discussed. It will be shown how diffuse feedbacks, based on this network, can improve the performance of a given type of immune effector cell, and can cause the preferential amplification of more potent effectors. It will be argued that diffuse feedback also acts in other biological systems ranging from the metabolic system to ant colonies.