Interaction of mannose binding lectin and other pattern recognition receptors in human corneal epithelial cells during Aspergillus fumigatus infection

Mannose binding lectin (MBL), a member of C-type lectin superfamily, plays a significant role in the innate immune system as one of the Pattern-Recognition Receptors (PRRs). This study investigated the relationship between MBL and other PRRs including Dectin-1and TLR2, and detected the reaction of MBL towards the expression of cytokines in human corneal epithelial cells (HCECs) and murine corneas upon Aspergillus fumigatus (A. fumigatus) hyphae infection. We found that MBL was significantly up-regulated in C57BL/6 corneas infected with A. fumigatus and HCECs incubated with A. fumigatus hyphae. Moreover, both of mRNA and protein levels of Dectin-1, TLR2, IL-1β and TNF-α were increased dramatically to peak point with the pretreatment of exogenous MBL, while decreased significantly with the pretreatment of MBL monoclonal antibody in HCECs. Pretreatment with laminarin and TLR2 neutralizing antibody decreased both of mRNA and protein levels of MBL and proinflammatory mediators (IL-1β and TNF-α) in A. fumigatus hyphae infected HCECs. These data demonstrate that A. fumigatus introduce the expression of MBL in human corneas, C57BL/6 corneas and HCECs. MBL, Dectin-1 and TLR2 interact with each other upon the treatment of A. fumigatus, and MBL contributes to the innate immune responses by regulating proinflammatory mediators, such as IL-1β and TNF-α.