Molecular biology of macrophage activation: a pathway whereby psychosocial factors can potentially affect health

Over the past decade, numerous links between the mind, the immune system, and the nervous system have been clearly elucidated in regard to the lymphoid elements of the immune system. Recently, attention has been given to the suggestion that such links exist to mononuclear phagocytes. The fundamental biology and physiology of these cells are clearly consonant with such a role. Mononuclear phagocytes bear receptors on their surface for numerous ligands, including neuroendocrine peptides and hormones. Furthermore, macrophages can be modulated by a variety of life-style choices such as smoking, ingestion of alcohol, and dietary lipid. Mononuclear phagocytes are key cells in the development of atherosclerosis and play significant roles in host protection against neoplasia and in the development of certain autoimmune diseases. In regard to atherogenesis, stress can potentiate the effects of a high lipid diet in initiating formation of the macrophage-laden lesions of early atherosclerosis. We have been able to show that oxidized lipids, acting in concert with stress as modeled pharmacologically in terms of catecholamines, induces a macrophage phenotype which would likely promote the development of atherosclerosis but lower host resistance to neoplasia. We are currently testing this hypothesis critically. Over the coming decade, it will be important for numerous investigators to examine the broad hypothesis that mononuclear phagocytes are one key element in the induction of psychosocially produced diseases. A clear understanding of the biology and molecular biology of these cells will provide a potent tool for analyzing these problems.