This, however, is in contrast with previous studies, which reported that eosinophils mainly secrete Th2-type cytokines in response to parasite antigens and allergens.33,34 The GM-CSF is a cytokine expressed by a variety of cells, including activated T cells, Mφ, fibroblasts and epithelial cells. GM-CSF

is required for the recognition of pathogens, the timely development and proper compartmentalization of the immune response and the control of pulmonary growth of C. neoformans.35 Furthermore, GM-CSF stimulates the functional activity of eosinophils and maintains the maximum viability of cells,13 and GM-CSF-activated BAY 57-1293 eosinophils have been reported to be capable of acting as specific APCs to a T-cell BMS-777607 order clone derived from mice infected with Mesocestoides corti.27 The results of the present study showed that

GM-CSF only modified the MHC class II expression levels on eosinophil surfaces cultured with C. neoformans. Moreover, C. neoformans-pulsed eosinophils in the presence of GM-CSF expressed threefold more MHC class II than C. neoformans-pulsed eosinophils in the absence of this stimulating factor (Fig. 2b). In contrast, GM-CSF did not modify phagocytosis of the fungus, the expression of MHC class I, CD80 or CD86, cytokine production or the fungicidal molecules released by eosinophils incubated with the fungus. Related to this, Feldmesser et al.19 have demonstrated that short-term incubation with IL-5, GM-CSF and lipopolysaccharide (LPS) did not appear to enhance eosinophil phagocytosis. Phagocyte–microbe contact is accompanied by intracellular signals that trigger cellular processes as diverse as cytoskeletal rearrangement, alterations in membrane trafficking, activation of microbial killing mechanisms, production of pro- and anti-inflammatory cytokines and chemokines, activation of apoptosis and the production of molecules required for efficient antigen presentation to the adaptive immune system.36,37 In this regard, it has been shown that eosinophils are able to produce H2O2 in response to phagocytosis

of heat-killed Staphylococcus aureus38 and excretory–secretory products (ESP) from interacting with Fasciola hepatica.8 In addition, Phipps et al.39 suggests that eosinophil-derived NO contributes to innate protection against the respiratory syncytial virus. In fact, in cryptococosis, the generation of NO is required ZD1839 in vivo for resistance to primary fungal infections. Moreover, mice deficient in inducible nitric oxide synthase (iNOS) did not survive a primary infection.40 Snelgrove et al.41 have shown that NADPH oxidase-deficient mice elicited a heightened Mφ-driven Th1 response with the containment of cryptococci within pulmonary granulomatous lesions. They also observed improved clearance of pathogen in lung and airways, with reduced dissemination to the brain. In the present study, opsonized C. neoformans down-regulated NO and H2O2 synthesis by eosinophils in an FcγRII-dependent manner.