Jawless fish such as lampreys and hagfish have a humoral immune system that shows close functional convergence with the B cells and antibodies of vertebrates but is structurally completely unrelated. In eLife, Herrin and colleagues compare the reponses of mouse immunoglobulin-based antibodies and a lamprey leucine-rich repeat–based antibody, VLR-B, to influenza virus. Immunization of lampreys generates highly specific VLR-B antibodies that, much like those in the mouse, are directed almost exclusively against the globular head of influenza virus hemagglutinin (HA). HA-specific lamprey antiserum is able to block infection with influenza virus in vitro and also compete with mouse antibodies for overlapping epitopes, which suggests a very similar immunodominance hierachy for these two very unrelated species. Therefore, despite the massive structural differences between VLR-B and immunoglobulin antibodies, unifying principles of antigen recognition seem to prevail.

eLife (30 July 2015) doi:10.1016/j.cell.2015.06.057