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Homegrown Defender: Urinary infections face natural guard

Bacteria are adept at sneaking past our defenses, succeeding most often when swallowed, inhaled, or given free passage via a cut or scratch. But over the past 2 decades, scientists have found that even before the immune system can gin up a response to such intruders, built-in antimicrobial agents in the intestines, lungs, and skin act as a first line of defense. A new study shows that one of these antimicrobial shock troops, a peptide called cathelicidin, patrols another portal as well—the urinary tract.

Cells that line the urinary tract all the way back to the kidneys churn out cathelicidin in response to bacterial invaders, researchers report in the June Nature Medicine. Furthermore, inflammatory cells later deliver a second dose of the antimicrobial peptide to those passages, the scientists say. By damaging the bacterial membrane, cathelicidin usually kills a microbe on contact.

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