
Full text loading...
Category: Clinical Microbiology; Fungi and Fungal Pathogenesis
Innate Defense against Aspergillus: the Phagocyte, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815523/9781555814380_Chap18-1.gif /docserver/preview/fulltext/10.1128/9781555815523/9781555814380_Chap18-2.gifAbstract:
Macrophages and neutrophils are essential components of the innate immune response of the host to infection by microorganisms. Macrophages have three main functions: (i) to take up and kill pathogens by phagocytosis; (ii) to generate a large array of biologically active molecules, including cytokines, chemokines, and lipid mediators, that orchestrate the recruitment of other phagocytes, such as monocytes and neutrophils; and (iii) to present antigens to lymphocytes. The innate immune system is the first line of host defense against pathogens. Macrophages and neutrophils constitute the bulwark of the innate immune system. The macrophages internalize microorganisms via different types of receptors expressed on their surface. These receptors bind pathogen-associated molecular patterns (PAMP) directly or via opsonins. Aspergillus fumigatus is recognized directly, via its carbohydrates, by DC-SIGN and dectin-1. Alveolar macrophages are important for the host defense against A. fumigatus, as demonstrated in a murine model of invasive pulmonary aspergillosis (IPA). As for alveolar macrophages, pathogen recognition is the first important step. Neutrophils express various toll-like receptors (TLRs) but have no TLR3. Alveolar macrophages and neutrophils are clearly of prime importance for combating inhaled A. fumigatus. Indeed, if for any reason these cells are absent or incapacitated, the fungus grows and causes a life threatening infection.
Full text loading...
Role of neutrophils and alveolar macrophages in experimental IPA. Mice were infected intratracheally with 107 (A) or 106 (B) conidia of A. fumigatus. Mice were depleted of neutrophils and macrophages by treatment with vinblastine ( Balloy et al., 2005b ) and chlodronate ( Chignard et al., 2007 ), respectively. (From Chignard et al. [2007] with permission of the publisher.)
Neutrophil recruitment and chitin concentration in the lung in experimental IPA. Mice were infected intratracheally with 107 conidia of A. fumigatus and BAL was obtained at various time points. Neutrophils were counted and chitin quantified. (Images courtesy of V. Balloy et al. [unpublished data].)