Mannan-binding lectin regulates Treg/Th17 cell balance in mice with Candida albicans infection
Objective 
To investigate the regulation of Treg/Th17 axis by mannan-binding lectin (MBL) in mice with Candida albicans (C.albicans) infection. 
 
 
Methods 
MBL gene-knockdown (MBL-/-) C57BL/6 mice and wild-type (WT) C57BL/6 mice were divided into four groups. C. albicans strains (2×107 CFU) were injected intraperitoneally into the mice of infection groups. Paraffin sections of mouse liver and kidney tissues were prepared on 3 d. Histopathological changes were observed with hematoxylin and eosin (HE) and Periodic acid-Schiff (PAS) staining. Flow cytometry was performed to analyze Th17 and Treg cells in mice on 7 d. The levels of IL-10 and IL-17A were measured by ELISA. CD4+ T cells were obtained from spleen cells by magnetic sorting. Expression of Foxp3 and RORγt at mRNA and protein levels were detected by qRT-PCR and Western blot, respectively. 
 
 
Results 
The mouse model of C. albicans infection was established successfully. After infection, the MBL-/- mice had higher percentages of Th17 cells, but lower percentages of Treg cells than the WT mice. ELISA results showed that compared with the WT mice with C. albicans infection, the MBL-/- mice had significantly increased IL-17A and decreased IL-10 after infection. Moreover, the expression of RORγt at both mRNA and protein levels was up-regulated, while that of Foxp3 was down-regulated in the MBL-/- mice than in the WT mice following infection. 
 
 
Conclusions 
MBL regulates the immune balance of Treg/Th17 cells in mice infected with C. albicans through promoting the differentiation of CD4+ T cells into Treg cell subsets and inhibiting the differentiation into Th17 cell subsets. 
 
 
Key words: 
Mannan-binding lectin (MBL); MBL gene-knockdown mice; Candida albicans; Th17 cell; Regulatory T cell