Do Antibodies Pack a Deadly Punch?

Abstract

A sk most people what antibodies do, and they'll respond that these immune agents kill bacteria, viruses, and other harmful microbes that seek to infect the body. An immunologist standing nearby would probably correct that answer by pointing out that antibodies don't actually do the dirty work. According to mainstream immunology, these Y-shaped proteins merely bind to bits of microbes. This targets the germs for destruction by other such as a family of proteins called complement, or by immune cells. In this view, one can think of an antibody as the laser beam that soldiers use to identify the target of a smart bomb. But what if these immune proteins carry a grenade or two with them? A recent study suggesting just that threatens to upset the traditional notion of what antibodies do. In the Sept. 26 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES, Richard Lerner of the Scripps Research Institute in La Jolla, Calif., and his colleagues report that almost every antibody they've tested can generate hydrogen peroxide from molecular oxygen. Since hydrogen peroxide-a widely used antiseptic-readily converts into toxic molecules that damage DNA and proteins, antibodies probably do more than passively label dangerous microbes for destruction, says Lerner. Antibodies themselves are germ killers, he contends. Lerner holds that his group's discovery compels a reassessment of the evolution and function of antibodies. Some investigators suggest that his findings complement their work showing various enzymatic properties of antibodies. Other scientists caution that, so far, there are no data showing that the vertebrate immune system depends on these chemical talents of antibodies or that it ever did in its evolutionary past. Nonetheless, some researchers are intrigued by these possibilities. Lerner's finding is very exciting because it suggests that antibodies have the potential to be microbicidal molecules, says immunologist Arturo Casadevall of Albert Einstein College of Medicine in New York City.