The cytokine‐inducing activities of fungal polysaccharides were examined in human monocytes in culture, with special reference to CD14 and Toll‐like receptors (TLRs). Tumor necrosis factor alpha (TNF‐α) production by monocytes was markedly induced in a dose‐dependent manner upon stimulation with cell walls from Candida albicans and mannan from Saccharomyces cerevisiae and C. albicans, although relatively high concentrations (10 to 100 μg/ml) of stimulants were required for activation as compared with the reference lipopolysaccharide (LPS) (1 to 10 ng/ml). The yeast form C. albicans and its mannan and cell wall fractions exhibited higher TNF‐α production than respective preparations from the hyphal form. Only slight TNF‐α production was induced by the S. cerevisiae glucan. The TNF‐α production triggered by reference LPS and purified fungal mannans required the presence of LPS‐binding protein (LBP), and these responses were inhibited by anti‐CD14 and anti‐TLR4 antibodies, but not by anti‐TLR2 antibody. In contrast to the activity of LPS, the activity of purified S. cerevisiae mannan was not inhibited by polymyxin B. These findings suggested that the mannan‐LBP complex is recognized by CD14 on monocytes and that signaling through TLR4 leads to the production of proinflammatory cytokines in a manner similar to that induced by LPS.

The culture supernatant of Candida albicans promoted the disruption of human red blood cells (RBCs). The haemolytic activity was detected in a sugarrich fraction (about 200 kDa) from Sephacryl S-100 chromatography. As the haemolytic activity was adsorbed by concanavalin A-Sepharose, the haemolytic factor may be a mannoprotein. The activity was inactivated by periodate oxidation, indicating that the sugar moiety of the mannoprotein played an important role in the haemolysis. The structure of the sugar moiety of the mannoprotein was identified as a cell-wall mannan by 'H-NMR analysis, and purified C. albicans mannan promoted the disruption of RBCs. The binding of mannan to RBCs was demonstrated by flow cytometric analysis and was inhibited by the addition of band 3 protein inhibitor, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). The haemolysis caused by mannan was inhibited by DIDS, SITS (4-acetamido-4'-isothiocyanatostiIbene-2,2'-disulfonic acid) and bis(sulfosuccinimidy1) suberate, but not by pyridoxal 5-phosphate. These results indicated that a mannoprotein released from C. albicans bound to the band 3 protein on RBCs, thereby promoting their disruption.

No abstract

N‐Acetylchitohexaose, a water‐soluble oligosaccharide was found to display a significant anti‐metastatic effect against Lewis lung carcinoma (LLC) transplanted into C57BL/6 mice, giving rise to a 40–50% inhibition ratio of pulmonary metastasis when administered intravenously (1 mg/kg) on day 6 after the tumor implantation (5 × 105 cells/mouse). It was also revealed that this hexaose had a significant growth‐inhibitory effect against the local tumor of the same carcinoma (a 20–30% inhibition ratio), showing an enhancing effect on concomitant immunity in local tumor‐resected mice. This oligosaccharide was also shown to enhance the tumoricidal effect of splenic T lymphocytes against LLC and P‐815 mastocytoma cells and to increase the natural killer activity of splenic T lymphocytes, assayed with YAC‐1 cells as the target.

No abstract