[Cytokines and their role as health and disease mediators. New approaches to old problems]

The cytokines are multifunctional polypeptide hormones, produced by a variety of cells, that participate in the regulation of many biological processes. Essentially acting as intercellular messengers, they play a central role in the maintenance of homeostasis in normal tissues. Cytokines are key mediators of both local and systemic immune-inflammatory responses; therefore, disturbances in their secretion, response and/or regulation have been implicated in the pathophysiology of several conditions in which an exaggerated auto-destructive component appears to play a role. Conversely, deficits in cytokine production probably impair the host's ability to mount an effective immune response and may underlie the increased susceptibility to microbial infection observed, for example, in the neonate or in the malnourished patient. A review of the principal aspects of the biology of cytokines is presented together with the evidence supporting their involvement in several pathological states and the potential therapeutic applications of these mediators as novel immunomodulating agents.