Unlike T-cells, which recognize linear epitopes presented by MHC molecules, B cells can recognize antigen in its native form. Antibody response against influenza infection is mediated by secretory IgA antibodies and serum IgG antibodies. IgA are transported across the mucosal epithelium of the upper respiratory tract, where they represent the first immunobarrier to influenza viruses. IgG transude from the serum to the mucus by diffusion and are primarily responsible for the protection of the lower respiratory tract [15] .