Dendritic cells (DCs) are potent antigen-presenting cells (APCs) that have emerged as key regulators of adaptive immunity (Immunity 31:412-424, 2009). The general function of lung DCs is to recognize and pick up foreign antigens at the outskirts of the body, and subsequently migrate with their cargo to the draining mediastinal lymph nodes where antigen is processed into immunogenic peptides and displayed onto MHCI and MHCII molecules for presentation to naïve T cells. In fact these cells should be seen as specialized cells of the mononuclear phagocyte system that have evolved from the cells of the innate immune system to control adaptive immunity that came later in evolution.