Objective To study the immunologic function of MAN2C1 gene in the transgenic mice.Methods Infection of transgenic mice with H5N1 were performed by nasal dripping.The pathological changes of lung tissues were observed by HE staining and immuno-histochemistry.H5N1 viral load in lung of mice were detected with RT-PCR.Serum antibody against H5N1 was measured with indirect ELISA.Results The pathological changes were more serious in the transgenic lung than that of control mice.The expression levels of H5N1 virus antigen and virus load in the lung tissues of transgenic mice were obviously higher than that in control mice. A decreased level of serum antibody against H5N1 was also observed in the transgenic mice compared with control mice.Conclusion Our results suggest that MAN2C1 gene down-regulates the humoral immunity against virus infection.