ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effects of mannan-binding lectin (MBL) on the functions of human polymorphonuclear cells (PMNs).</p><p><b>METHODS</b>ELISA and Dot blot were performed to examine the binding between MBL and the microorganisms. Flow cytometry and fluorescence microscopy were employed to analyze the phagocytosis of FITC-labeled microorganisms by the PMNs. Real-time quantitative PCR was used to detect the expression levels of IL-1β, TNF-α and CD11b mRNA in the PMNs, and ELISA used to detect the levels of TNF-α and IL-6 in the supernatants of PMN culture. Nitro-blue tetrazolium reduction assay was used to estimate the levels of superoxide production.</p><p><b>RESULTS</b>MBL bound to the microorganisms in a dose-dependent manner. MBL had no significant effect on phagocytosis of C. albicans and E.coli by the PMNs in the absence of human serum, but in presence of mixed MBL-deficient human sera, MBL promoted the phagocytosis of C. albicans, which could be blocked by mannan. Mannan treatment increased the expressions of IL-1β, TNF-α, IL-6 and CD11b and enhanced superoxide production in the PMNs.</p><p><b>CONCLUSION</b>MBL can promote phagocytosis of microorganisms by PMNs and increase the expressions of proinflammatory cytokines from PMNs in a complement lectin pathway-dependent manner.</p>