How do white blood cells know where the bacteria is?

Question by Luna Lovegood ????????: How do white blood cells know where the bacteria is?
I just watched a video of a white blood cell chasing bacteria.
http://www.youtube.com/watch?v=JnlULOjUhSQ < --that is the video i watched.
But how does it sense were it is? Can it see the bacteria? Smell? How does it know where the bacteria is and is travelling?


Best answer:
Answer by LilaNo, it cannot sense it.

However, there are enough white blood cells in the bloodstream that they 'meet' each

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