'More diversity in their antibodies'Antibodies are Y-shaped proteins that help the immune system recognize and neutralize foreign invaders, including viruses, as well as other threats, like toxins. The team then showed that both sets of genes were functional and actively used by immune cells to build antibodies. Those changes can help antibodies become more "customizable" to whatever threatens the immune system, Frank said. The adaptive immune system is more like the heroine Mulan: highly targeted and capable of responding to a specific enemy, but slower to develop. This degree of customization could help the bats immune system ward off a wider range of threats than other mammals can.