Neuroendocrine and immune interactions with airway macrophages

Immune cells, including macrophages, are sources of many cytokines as well as a number of peptide hormones such as corticotropic releasing hormone and the endorphins. These mediators are involved in local immune regulation and may also function in an endocrine manner to influence the systemic hormonal response to stress. In turn, the major effectors of the systemic stress response, namely the glucocorticoids and the catecholamines, have been shown to modulate macrophage function. This review highlights some of what is known about neuroendocrine interactions with macrophages, and in particular, with airway macrophages, as modulation of airway macrophage function by neuroendocrine peptides is likely critical for the maintenance of lung homeostasis. The production of neuromediators (acetylcholine, catecholamines, sensory neuropeptides) and neuropeptide hormones (i.e. adrenocorticotropic hormone (ACTH) and beta-endorphin), from airway macrophages is also discussed. We have defined airway macrophages as those cells that reside in the airway compartment (i.e. versus the interstitium) and provide the first line of defence to inhaled particles.