Isolation of mouse lung dendritic cells.

Lung dendritic cells (DC) play a fundamental role in sensing invading pathogens (1,2) as well as in the control of tolerogenic responses (3) in the respiratory tract. At least three main subsets of lung dendritic cells have been described in mice: conventional DC (cDC) (4), plasmacytoid DC (pDC) (5) and the IFN-producing killer DC (IKDC) (6,7). The cDC subset is the most prominent DC subset in the lung (8). The common marker known to identify DC subsets is CD11c, a type I transmembrane integrin (β2) that is also expressed on monocytes, macrophages, neutrophils and some B cells (9). In some tissues, using CD11c as a marker to identify mouse DC is valid, as in spleen, where most CD11c(+) cells represent the cDC subset which expresses high levels of the major histocompatibility complex class II (MHC-II). However, the lung is a more heterogeneous tissue where beside DC subsets, there is a high percentage of a distinct cell population that expresses high levels of CD11c bout low levels of MHC-II. Based on its characterization and mostly on its expression of F4/80, an splenic macrophage marker, the CD11c(hi)MHC-II(lo) lung cell population has been identified as pulmonary macrophages 10 and more recently, as a potential DC precursor (11). In contrast to mouse pDC, the study of the specific role of cDC in the pulmonary immune response has been limited due to the lack of a specific marker that could help in the isolation of these cells. Therefore, in this work, we describe a procedure to isolate highly purified mouse lung cDC. The isolation of pulmonary DC subsets represents a very useful tool to gain insights into the function of these cells in response to respiratory pathogens as well as environmental factors that can trigger the host immune response in the lung.