Mann-Whitney and Wilcoxon signed rank tests were performed using GraphPad Prism (GraphPad Software Inc, La Jolla, CA). A p-value of #0.05 was considered significant. Figure S1 pDC gating strategy. (A-D) pDCs were defined in these studies as amine -(viable) lineage -HLA-DR + CD11c -CD123 + cells. (E) Representative FACS plot demonstrating BDCA2 vs. NSP2 staining of pDCs (red) vs. contaminating HLA-DR-(blue) cells exposed to RRV (n = 12). Found at: doi:10.1371/journal.ppat.1000931.s001 (0.39 MB TIF) Role of CD14 in lung inflammation and infection This article is one of ten reviews selected from the Yearbook of Intensive Care and Emergency Medicine 2010 (Springer Verlag) and co-published as a series in Critical Care. Other articles in the series can be found online at http://ccforum.com/series/yearbook. Further information about the Yearbook of Intensive Care and Emergency Medicine is available from http://www.springer.com/series/2855. Toll-like receptors (TLR) on the surface of cells of the respiratory tract play an essential role in sensing the presence of microorganisms in the airways and lungs. Th ese receptors trigger infl ammatory responses, activate innate immune responses, and prime adaptive immune responses to eradicate invading microbes [1] . TLR are members of a family of pattern-recognition receptors, which recognize molecular structures of bacteria, viruses, fungi and protozoa (pathogen-associated molecular patterns or PAMPs), as well as endogenous structures and proteins released during infl ammation (damage/ danger-associated molecular patterns or DAMPs). To date, ten diff erent TLR have been identifi ed in humans and twelve in mice. TLR are expressed on all cells of the immune system, but also on parenchymal cells of many organs and tissues. Th e binding of a PAMP to a TLR results in cellular activation and initiates a variety of eff ector functions, including cytokine secretion, prolifera tion, co-stimulation or phagocyte maturation. To facilitate microbial recognition and to amplify cellular responses, certain TLR require additional proteins, such as lipopolysaccharide (LPS) binding protein (LBP), CD14, CD36 and high mobility group box-1 protein (HMGB-1). In this chapter, the role of CD14 as an accessory receptor for TLR in lung infl ammation and infection is discussed. Th e central role of CD14 in the recognition of various PAMPs and amplifi cation of immune and infl ammatory responses in the lung is depicted in Figure 1 .