MBL2 and influenza: Sera and respiratory fluids of mammals contain several innate soluble factors that exhibit anti-influenza activity, for examples, members of the collectin superfamily such as surfactant protein A (SP-A), surfactant protein D (SP-D), conglutinin and mannose-binding lectin (MBL) [11]–[13], member of the pentraxin superfamily such as pentraxin 3 (PTX3) [14], and serum amyloid P component [15].