Like police using tear gas to quell a riot, immune system cells that throw corrosive chemicals on invading bacteria may use a kind of chemical gas mask to protect themselves--and healthy tissue--from their own weapon. Scientists have found that vitamin C may serve as just such a shield to save a key type of immune cell from self-annihilation, according to a report in the 9 December Proceedings of the National Academy of Sciences.

Immune cells called neutrophils destroy bacteria with a two-stage attack: First, they produce oxidants that puncture a bacterium's cell walls, then the neutrophils engulf the disabled bug. Recent work by Mark Levine's group at the National Institutes of Health has hinted that neutrophils may avoid poisoning themselves by absorbing extra ascorbic acid, or vitamin C, which can neutralize oxidants.

To test this theory, a team led by Levine and Yauhui Wang collected neutrophils from people with bacterial infections and incubated the cells for up to an hour in two sets of dishes stocked with vitamin C and nutrients. One set was infected with bacteria; the other was clean. Within 20 minutes, the neutrophils from the infected dishes had accumulated up to 30 times more vitamin C than those in bacteria-free dishes. The researchers also found that neutrophils from people with the rare chronic granulomatous disease, which makes them especially vulnerable to bacterial infections, did not accumulate vitamin C when confronted with bacteria.

Vitamin C stockpiling "could be a very clever way that the neutrophils protect themselves," says biologist John Curnutte of Genentech Inc. in San Francisco. But he and Levine caution that neutrophils may behave differently in the body than in the lab. The key question, adds cell biologist Sam Silverstein of Columbia University in New York City, is whether dosing up on vitamin C makes a person's neutrophils better bacteria killers. If so, Levine says, vitamin C could be an approach to tackling antibiotic-resistant bacteria.