Binding and uptake of Candida albicans by human monocyte-derived dendritic cells

The innate immune response was once considered to be limited to basic and unspecific "ingest and kill" mechanisms that would provide the first anti-microbial defense before the specific humoral and cellular immune response was mounted. In the last decade, however, several families of pattern-recognition receptors (PRRs) have been identified that have substantially revolutionized our understanding of host-pathogen interactions, which turned out to be highly specific and dynamic. The central players in this process are the antigen-presenting dendritic cells (DCs), which express a variety of membrane-associated as well as cytosolic PRRs, each able to sense specific molecular patterns present at the surface of microorganisms and to transduce specific signals that activate the DCs. The present challenge is to dissect the complex interactions between the PRR repertoire of the host DCs and the invading pathogens. In this chapter, we describe a flow cytometry-based assay that allows the quantification of binding of the pathogenic fungus Candida albicans specifically by human monocyte-derived DCs. Furthermore, we provide a protocol to visualize PRRs that are involved in the uptake of C. albicans using fluorescently labeled antibodies and confocal microscopy. Both methods can be applied to determine binding and uptake of other pathogens by different types of immune cells.