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,
- PDF / 447,016 Bytes
- 13 Pages / 504.57 x 720 pts Page_size
- 28 Downloads / 187 Views
Introduction In healthy individuals, the innate immune system efficiently provides protection from the numerous fungal species that normally coexist with humans. Candida albicans is a commensal fungus that colonizes the skin and the mucosal surfaces of healthy individuals, without causing disease. However, when host defense mechanisms are compromised, as is the case for patients undergoing chemotherapy or organ transplantation, C. albicans can become the cause of life-threatening fungal infections (1).
Alexandra C. Brand and Donna M. MacCallum (eds.), Host-Fungus Interactions: Methods and Protocols, Methods in Molecular Biology, vol. 845, DOI 10.1007/978-1-61779-539-8_21, © Springer Science+Business Media, LLC 2012
319
320
A.B. van Spriel and A. Cambi
Until recently, little was known about the mechanisms used by DCs, the major players in linking innate and acquired immunity, to recognize C. albicans as a pathogenic microorganism, or how this interaction triggered an inflammatory immune response. In the past decade, more insights have been gained into the specific recognition of various classes of microorganisms by the innate immune system, and in particular the important role of antigen-presenting DCs in fungal recognition (2–6). DCs sense invading pathogens through so-called pattern-recognition receptors (PRRs), which recognize conserved microbial chemical signatures generally referred to as pathogen-associated molecular patterns (PAMPs) (7). The cell wall of C. albicans is a well-defined architecture of several types of polysaccharide chains, including mannan, betaglucan, and chitin, which are arranged in different layers to confer rigidity and stability to the fungal surface (8, 9). Since the mannans are localized at the outermost layer, mannan detection represents one of the first steps in the recognition of C. albicans by the host innate immune cells. In addition, beta-glucan moieties, which can extend at specific sites through the mannan layer and reach the surface of the cell wall, also activate the immune system (10). The two major classes of PRRs on DCs that mediate fungal recognition are the Toll-like receptors (TLRs) (11) and the C-type lectin-like receptors (CLRs) (12). In particular, TLR2 senses phospholipomannan (13), while TLR4 recognizes O-linked mannans (14). The primary CLRs that recognize fungal polysaccharide structures are the beta-glucan receptor Dectin-1 (10) and the macrophage mannose receptor (MR) and the dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN) both recognizing mannan moieties (2, 5). Clearly, a well-orchestrated network of different PRRs mediates the interactions between C. albicans and the DCs. To dissect the specific contribution of each receptor, we have established a flow cytometry-based binding assay that enables determination of the percentage of DCs able to bind to C. albicans cells. The use of a variety of inhibitors allows the determination of the specific contribution of each PRR involved in this interaction. Furthermore, whereas the TLRs exclusively s
Data Loading...
