Circumcision may bolster immune system against harmful bacteria

LA Times   Circumcision is known to reduce a man's risk of HIV infection by at least half, but scientists don't know why. A new study offers support for the theory that removing the foreskin deprives troublesome bacteria of a place to live, leaving the immune system in much better shape to keep the human immunodeficiency virus at bay.

Anyone who has ever lifted a rock and watched as the earth beneath it was quickly vacated by legions of bugs and tiny worms would be familiar with the principle, said study leader Dr. Cindy Liu: After the foreskin is cut away, the masses of genital bacteria that once existed beneath it end up disappearing.

"It's the same as if you clear-cut a forest," said Liu, a pathologist at the Translational Genomics Research Institute in Flagstaff, Ariz. "The community of animals that once lived in that forest is going to change."

Of particular note is that circumcision undercuts anaerobic bacteria, the microbes that thrive in oxygen-deprived environments, she said. By reducing the number of anaerobic bacteria, the body's immune cells may be better able to destroy the virus — and less likely to fall prey to its Trojan horse-style of attack, the authors suggest.