Immune evasion by chytrid fungal pathogens includes macrophages 2669

Abstract Description Amphibians continue to experience global population declines due to chytridiomycosis caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Although amphibians have robust immune defenses, this pathogen appears to have evolved counter defenses that permit it to survive in amphibian skin. Previous studies showed that Bd cells or cell-free supernatants inhibited lymphocytes by induction of apoptosis, suggesting impaired local cell killing. However, there is little evidence for lymphocyte recruitment to chytrid-infected skin, suggesting that the fungus may also inhibit functions of antigen presenting cells. The capacity of peritoneal leukocytes (PLs) enriched in macrophages (Mfs) and neutrophils to phagocytose pHrodo™ Green Zymosan BioParticles™ was significantly reduced by co-culture with Bd cells. Cell-free supernatants produced by Bd also inhibited uptake of pHrodo™ Red Staph aureus BioParticles™. The phagocytic capacities of frog bone marrow-derived Mfs, differentiated by colony stimulating-factor-1- or interleukin-34 (key Mf growth factors), as well as a mammalian Mf cell line, were also impaired by Bd. Inhibition of mammalian Mfs suggests that the functions of the inhibitory factors are not restricted to amphibian cells. These findings suggest that Bd cells and cell-derived factors can inhibit recognition by Mfs that reside in or would enter the skin compartment to begin the process of clearing a Bd infection. Support: NSF 2147466 (LG) and 2147467 (to LR-S). Funding Sources Supported by NSF 2147466 ( to LG) and 2147467 (to LR-S) Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)