What is the definition of Mainland Blood Cells?

"Mainland blood cells are the unsung heroes of our circulatory system, but let's get this off their chest for a sec. They're the blood cells from the non-Islanders - that's, you know, the folks living on the mainland. They're usually more focused on avoiding the 'Island Blood Crisis' and don't get caught in the 'Island Fever' of needing platelets or white blood cells from the other side."

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Edgy example sentence: "The detective couldn't shake off the mainland blood cell suspicion, convinced the rogue cells were plotting to steal his city's supply of pizza."