Consider them the guardian angels of your small intestine.
Long known as Paneth cells, these sentries inhabit tiny pits in the intestine called crypts. Scientists now offer the best evidence yet that these cells defend other cells in the crypts by discharging bacteria-killing bursts of enzymes and other molecules.
Protecting the crypt's so-called stem cells, which replenish the lining of the small intestine, is vital. With a surface area about the size of a football field, the lining is continually damaged by digestive enzymes and bile. It must therefore turn over rapidly, every few days in a person.
It's up to the stem cells, which dwell just above the Paneth cells, to spawn progeny that migrate onto the tips of fingerlike villi that line the intestine and absorb nutrients.
For years, scientists have amassed a case that Paneth cells safeguard stem cells. They initially found that Paneth cells contain stores of lysozyme, an enzyme that breaks down bacterial