Division of labor between lung dendritic cells and macrophages in the defense against pulmonary infections.

The lung is highly exposed to the external environment. For this reason, the lung needs to handle a number of potential threats present in inhaled air such as viruses or bacteria. Dendritic cells (DCs) and macrophages (MFs) play an important role in orchestrating the immune responses to these challenges. The severe lung inflammation caused by some pathogens poses a unique challenge to the immune system: the potential insult must be eliminated rapidly whereas tissue inflammation must be controlled in order to avoid collateral damages that can lead to acute respiratory failure. Immune responses to infectious agents are initiated and controlled by various populations of antigen-presenting cells with specialized functions, which include conventional DCs (cDCs), monocyte-derived DCs (moDCs), plasmacytoid DCs (pDCs), and alveolar MFs (AMFs). This review will discuss the role of these different cells in responses to pulmonary infections, with a focus on influenza virus and Mycobacterium tuberculosis.