Abstract
It is increasingly recognised that the immune and nervous systems are closely integrated to optimise defence systems within the lung. In this commentary, the contribution of various neuropeptides such as substance P, calcitonin gene-related peptide, vasoactive intestinal peptide and somatostatin to the regulation of T cell activation is discussed. These neuropeptides are released not only from nerve endings but also from inflammatory immune cells such as monocytes, dendritic cells, eosinophils and mast cells. On release they can exert both direct stimulatory and inhibitory effects on T cell activation and also indirect effects through their influence on the recruitment and activation of professional antigen-presenting dendritic cells. Neuropeptides should therefore be included in the conceptual framework of the immune regulation of T cell function by dendritic cells.