ABSTRACT
Dectin-2 is a C-type lectin receptor that recognizes high mannose polysaccharides. Cryptococcus neoformans, a yeast-form fungal pathogen, is rich in polysaccharides in its cell wall and capsule. In the present study, we analyzed the role of Dectin-2 in the host defense against C. neoformans infection. In Dectin-2 gene-disrupted (knockout) (Dectin-2KO) mice, the clearance of this fungus and the inflammatory response, as shown by histological analysis and accumulation of leukocytes in infected lungs, were comparable to those in wild-type (WT) mice. The production of type 2 helper T (Th2) cytokines in lungs was higher in Dectin-2KO mice than in WT mice after infection, whereas there was no difference in the levels of production of Th1, Th17, and proinflammatory cytokines between these mice. Mucin production was significantly increased in Dectin-2KO mice, and this increase was reversed by administration of anti-interleukin 4 (IL-4) monoclonal antibody (MAb). The levels of expression of ß1-defensin, cathelicidin, surfactant protein A (Sp-A), and Sp-D in infected lungs were comparable between these mice. In in vitro experiments, IL-12p40 and tumor necrosis factor alpha (TNF-α) production and expression of CD86 and major histocompatibility complex (MHC) class II by bone marrow-derived dendritic cells and alveolar macrophages were completely abrogated in Dectin-2KO mice. Finally, the disrupted lysates of C. neoformans, but not of whole yeast cells, activated Dectin-2-triggered signaling in an assay with nuclear factor of activated T cells (NFAT)-green fluorescent protein (GFP) reporter cells expressing this receptor. These results suggest that Dectin-2 may oppose the Th2 response and IL-4-dependent mucin production in the lungs after infection with C. neoformans, and it may not be required for the production of Th1, Th17, and proinflammatory cytokines or for clearance of this fungal pathogen.
Subject(s)
Cryptococcosis/immunology , Cryptococcus neoformans/immunology , Lectins, C-Type/genetics , Th2 Cells/immunology , Animals , Antibodies, Monoclonal/immunology , Antimicrobial Cationic Peptides/biosynthesis , B7-2 Antigen/biosynthesis , Cells, Cultured , Defensins/biosynthesis , Dendritic Cells/immunology , Female , Green Fluorescent Proteins/genetics , Histocompatibility Antigens Class II/biosynthesis , Inflammation/genetics , Inflammation/immunology , Interleukin-12 Subunit p40/biosynthesis , Interleukin-4/immunology , Lectins, C-Type/immunology , Lung/microbiology , Lung/pathology , Lung Diseases, Fungal/immunology , Macrophages, Alveolar/immunology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mucins/biosynthesis , Pulmonary Surfactant-Associated Protein A/biosynthesis , Pulmonary Surfactant-Associated Protein D/biosynthesis , Th1 Cells/immunology , Th17 Cells/immunology , Tumor Necrosis Factor-alpha/biosynthesis , CathelicidinsABSTRACT
A new diterpenoid was isolated from the leaves of Clerodendron trichotomumThunb. (Verbenaceae) along with one each of a known diterpenoid, phenylethanoid glycoside, and sterol and two known flavonoids. Their chemical structures were characterized on the basis of spectroscopic data and X-ray analysis. In addition, their antioxidant activities were evaluated using four different analyses.