What is the definition of Challenged Blood Cells?

Challenged blood cells are like the underdogs of the immune system - they're out there fighting off invaders, but when you throw in a little extra stress, like an autoimmune disorder or a nasty infection, they're thrown out the door for a second chance. It's like they've just won an unfair battle and are now trying to prove their worth in a barrage of 'Who's the real champion here?' moments.

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Edgy example sentence: "In the battle of the bloodlines, our once mighty challenged cells were sent packing by a sneaky autoimmune villain named 'Me,' leaving the body's defense army to wonder if they've been outplayed in a chess match with a napkin."