Early studies in murine models of influenza infection suggested that there might be “intermolecular” CD4 help for antibody responses, where the CD4 T cells and and B cells recognized different protein antigens (81, 82), However, in a vaccinia virus mouse model it was shown clearly that “intramolecular” CD4 help was required for antibodies to each individual viral protein from this large poxvirus (83). Here, CD4 is linked to influenza.