University of Alabama at Birmingham Jul 11 2025 At the surface, the immune response to a flu virus is simple. Some cells recognize the pathogen and send a signal to the immune system, and immune cells produce a potentially lifesaving antibody against the virus. Antigen in, antibody out. However, details of the intervening steps, as researchers have learned in the past 65 years, are quite complex - certain cells carry the flu antigen to the immune system, specific immune cells respond to the