Alexa 'Lex' Woods: How do you say "scared shitless" in Italian?
Sebastian de Rosa: Non vedo l'ora di uscire da questo piramide con te, perché mi sto cagando addosso. More or less.
Alexa 'Lex' Woods: Where exactly on the ice is this?
Charles Bishop Weyland: It's not on the ice, it's 2000 feet under it.
Sebastian de Rosa: I think this is a manhood ritual. The humaniod ones, they've been sent here to prove that they're worthy to become adults.
Alexa 'Lex' Woods: You're saying, they're, what, teenagers?
Charles Bishop Weyland: Seven days ago, one of my satellites over Antarctica, discovered a pyramid.
Sebastian de Rosa: When that door opens, we're dead.
Alexa 'Lex' Woods: Not if we set things right.
Sebastian de Rosa: What do you mean?
Alexa 'Lex' Woods: This pyramid, it's like a prison. We took the guards' guns, and now the prisoners are running free. To restore order, the guards need their guns.
Answer: When they emerged from the underground pyramid unscathed, the Predators assumed they were not infected. Any Predator, young or old, would have been taught to self destruct rather than be caught or killed. As seen in the previous movies. Lex was given the mark of a warrior, they assumed she was taught their code of honor.