Neuroimmune networks and aging of the immune system: biological and clinical significance

Over the past few years the concept of a bidirectional communication between the hypothalamus-pituitary-adrenal axis (HPAA) and the immune system has been reinforced by several experimental and clinical evidences. In this framework, recent studies have provided evidence that nerve cells and leukocytes release similar substances, e.g. cytokines, neurohormones and neuropeptides and, at the same time, these cells also bear specific receptors for the above substances. Additionally, it is well known that stressful life events, phobic disorders and migraine are characterized by profound deficits of host immune responsiveness. On these grounds, here emphasis has been placed on the aging phenomenon in which both nervous and immune cells are affected in terms of reduced percentage and functional activities. The overall data suggest that in aged people there is occurrence of several deficits of non-specific and specific immune responses, however, one has to take into consideration a possible alteration of the neuro-immune network in elderly. Therefore, life stresses or neuropsychiatric disorders could aggravate immune dysfunctions in aged individuals, this implying the need for therapeutical approaches able to improve both HPAA and immune functions.