After being sneezed on, Veronica is worried she will catch a sickness.
Ewww, cover your mouth, sicko.
Veronica breathed in his germs and her mucous was the first line of defense to try and stop the invaders from entering her body.
But, the antigen was able to defeat the, non-specific, first line of defense and now she is feeling very sick.
Now that the antigen is invading Veronica's body, her second line of defense kicks in. She begins to experience an imflammatory response.
Veronica starts to feel worse and worse. She can barely get out of bed because she feels weak and has a fever. Her third line of defense kicks in, and this time it's specific. Her antibodies directly target the invader for an attempt of final elimination.
Veronicas immune system was not strong enough to fight off the antigens. She became deathly ill and did not make it through the night. The Incredible Invaders won this time.