henry copeland:

Antibiotics found to weaken body's ability to fight off disease -- ScienceDaily

"Neutrophils play an important role as a first-line 'innate immune response' when foreign pathogens invade," said researcher Koji Watanabe, PhD. "We found that antibiotic disruption of the natural microbes in the gut prevented this from happening properly, leaving the gut susceptible to severe infection."
- www.sciencedaily.com