"Reporting in the current issue of the journal Science, researchers from Massachusetts General Hospital and Harvard Medical School describe studies showing that the spleen is a reservoir for huge numbers of immune cells called monocytes, and that in the event of a serious trauma to the body like a heart attack, gashing wound or microbial invasion, the spleen will disgorge those monocyte multitudes into the bloodstream to tackle the crisis.

"The parallel in military terms is a standing army," said Matthias Nahrendorf, an author of the report. "You don't want to have to recruit an entire fighting force from the ground up every time you need it."

That researchers are only now discovering a major feature of a rather large organ they have been studying for at least 2,000 years demonstrates yet again that there is nothing so foreign as the place we call home.

"Often, if you come across something in the body that seems like a big deal, you think, 'Why didn't anybody check this before?' " Dr. Nahrendorf said. "But the more you learn, the more you realize that we're just scratching on the surface of life. We don't know the whole story about anything." "

NYT