S2). In addition, IFN-γ production by naive T cells incubated with C. neoformans-pulsed eosinophils was similar to controls (Fig. 8a).

However, the production of TNF-α by these cells showed a significant increase in the presence of C. neoformans-pulsed or unpulsed eosinophils (Fig. 8b). Finally, we decided to investigate which T-cell population (CD4+ or CD8+) was involved in the production of IFN-γ and TNF-α. Surprisingly, only C. neoformans-primed CD8+ T cells cultured with C. neoformans-pulsed eosinophils produced IFN-γ. However, when both primed CD4+ T cells and CD8+ T cells were incubated with C. neoformans-pulsed eosinophils, large amounts of IFN-γ and TNF-α were produced (Fig. 8c,d). These results suggest that cooperation between C. neoformans-primed CD4+ and CD8+ T cells is very important in the case of IFN-γ and BAY 80-6946 manufacturer necessary for TNF-α production in the presence of C. neoformans-pulsed eosinophils. C. neoformans-pulsed eosinophils not only stimulated the proliferation of C. neoformans-primed

CD4+ and CD8+ T cells, but also produced a Th1 microenvironment where cooperation between these two T-cell populations could take place. This study provides the first evidence that rat eosinophils are capable of phagocytosing and presenting C. neoformans antigens to primed T cells, which then trigger a fungal-specific Th1 immune response. Eosinophils have been shown to be components of the inflammatory response to C. neoformans infection in the rat lung,3 and we have previously MK-8669 observed the presence of a large Casein kinase 1 number of eosinophils in the granulomas surrounding C. neoformans-encapsulated

yeasts during disseminated cryptococosis in rats (unpublished data). Moreover, although rat peritoneal eosinophils are unable to significantly phagocytose C. neoformans in vitro in the absence of opsonizing antibody, initial phagocytosis is rapidly completed in the presence of a specific mAb as an opsonin.19 Eosinophils constitutively express a variety of Fc receptors, including FcγRII, FcεRII and FcαR, with this expression varying according to the cytokine stimulation. Cross-linking of Fc receptors results in a variety of effects, including the induction of cytotoxicity, phagocytosis, immune complex binding and respiratory burst.19 Herein, we have demonstrated that eosinophils phagocytose opsonized live yeasts of C. neoformans and that this phenomenon involves the engagement of FcγRII and CD18, because the blocking of these receptors together caused the almost complete inhibition of fungal phagocytosis. These results are in agreement with previous reports which showed that Mφ and dendritic cells take up C. neoformans yeasts and the capsular polysaccharide via FcγRII and CD18.23,25,31,32 Furthermore, our results demonstrate that the phagocytosis of opsonized C.