What is the definition of Trained Blood Cells?

"Trained blood cells? Like, imagine they've been taught to do double duty - one day as your loyal bodyguards and the next, a secret agent in a bloodthirsty suit. They're trained to detect scents, remember faces, and even wield a scalpel. But here's the kicker - they've been conditioned to attack when they sense a slight drop in oxygen, not because they're on a bloodthirsty mission, but because that's how they were programmed to react when they first got their blood drawn for the first time."

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Example sentence: "After the marathon, the trainer's blood cells went on strike and decided to 'wap' with the regular ones, starting a new career as the city's most unsettling traffic jam conductor."