How immune cells quickly and efficiently capture influenza vaccines to trigger protective antibody responses is presented in a study published online this week in Nature Immunology.
Antigen-presenting dendritic cells (DCs) are immune cells that capture and process antigens ― in this case the inactivated form of influenza used in vaccines ― and present bits of these antigens to activate other immune cells, such as B cells.
Michael Carroll and Shannon Turley found that DCs in draining lymph nodes latch onto sugars present on the viral surface. This sugar recognition is achieved by a receptor called SIGN-R1. Blocking SIGN-R1 inhibited DC recognition of the influenza viruses, and more importantly blunted the ensuing antibody response by nearby B cells ― the cells responsible for antibody production. The scientists also visualized live DC movement in the lymph nodes of mice immunized with the influenza virus. Prior to immunization, the lymph node DCs were immobile, but upon catching the inactive lymph-borne virus using their SIGN-R1 receptors, the DCs became motile and migrated toward follicular areas rich in B cells.
This efficient DC capture of virus and delivery to B cells ensures rapid antibody responses can occur, which is necessary to combat fast-replicating pathogens such as live influenza virus.