Intercollege Physiology Program, Noll Physiological Research Center and Department of Kinesiology, Pennsylvania State University, University Park, PA 16802-6900.
During infection, inflammatory cytokines induce regulated changes in the host's internal milieu that create a hostile environment to an invading pathogen. Recent evidence indicates that these cytokines are constitutively produced, their production is increased by environmental stressors other than microbes, and they modulate "normal" physiological processes.