Immune-Neuro-Endocrine Interactions: Facts and Hypotheses

I. IntroductionTHE existence of mechanisms that provide immunity to an infective agent was inferred from empirical observations obtained through the ingenuity and deductive capacity of early investigators. The first procedures for vaccinations and serotherapy resulted from these observations. The implementation of these procedures, probably the most important contribution of immunology to medical science, was, at first, based on a very rudimentary knowledge of the immune system. During the first half of the 20th century, this rather primitive knowledge coincided with evidence showing that the endocrine and nervous systems integrate and regulate different bodily functions. Therefore, based on some supportive data, it was considered that immune mechanisms may also be influenced by these systems. However, at the beginning of the second half of the 20th century, most efforts were directed at understanding the molecular and cellular basis of the immune response and the mechanisms of acquisition of immunological diversity and self-tolerance.