ABSTRACT
Much of the research on immune regulation over the last 20 years has focused on the study of cellular functions and interactions in vitro. Although in vivo studies clearly have supported most in vitro-derived models of regulation, this approach tells only part of the story of immune regulation. The in vitro studies generally employ artificial media containing serum, often from a different species; they cannot offer a dynamic fluid environment akin to that which exists in vivo. It is now evident that the immune system operates in vivo with a homeostatic milieu replete with neurologic, neuroendocrine, endocrine, and micro-environmental regulatory influences clearly as complex as those regulating the internal networks of intercommunication among the cells of the system.
