More ways mother's milk fights disease.

For decades, pediatricians have touted the advantages of breast- feeding. Not only does it promote mother-infant bonding, they argue, it also transfers many of a woman's disease-fighting antibodies to her baby.

But microbiologists have long suspected there was more to the story. Reporting in Atlanta at Experimental Biology '95, several teams confirmed this week that mother's milk indeed delivers not just antibodies, but a battery of additional infection-fighting agents.

Among them are retinoic acids, a family of vitamin A derivatives. Charles E. Isaacs and his colleagues at the New York State Institute for Basic Research on Staten Island infected cultures of cells with a herpesvirus, then measured how rapidly the virus colonized untreated cultures and cultures treated with beta-carotene, retinoic acids, or one of several other vitamin A derivatives in breast milk.

Only the retinoic acids conferred any protection. After 48 hours, two types had each reduced the rate of viral colonization to one-hundredth that seen in unprotected cells; another reduced it to a ten-thousandth of the unprotected rate.

Isaacs emphasizes that the retinoic acids don't kill herpes. His group selected this virus to model the likely responses of many others. "But by slowing down the rate of viral replication, you're helping the immune system," he notes. "With retinoic acid in your body, you might only have to fight 50 virus particles instead of 50,000 or 100,000."

Olle Hernell of the University of Umea, in Sweden, and his coworkers focused on Helicobacter pylori. This bacterium, responsible for many stomach ulcers in adults, can also infect children.

Earlier research had shown that certain glycoproteins-- carbohydrate-carrying proteins--can inhibit the ability of this bacterium to attach to the stomach lining. The researchers therefore tested the glycoprotein kappa-casein, one of the two primary proteins in breast milk, in cultures of the mucus- secreting cells that line the stomach. They found, notes coauthor Bo Lonnerdal of the University of California, Davis, that "H. pylori didn't attach."

In the gastrointestinal tract of children receiving kappa-casein from mother's milk, Lonnerdal now suspects, the bacteria "would also wash out instead of attaching--and therefore become harmless."

Although cow's milk contains even more kappa-casein than breast milk, the bovine form "doesn't have any effect whatsoever on the virus," Lonnerdal says. Why not? Because the cow's glycoprotein has a different carbohydrate.

Breast milk also contains large quantities of interleukin-10 (IL-10), an immune system molecule that inhibits inflammation, report Roberto Garofalo and his colleagues at the University of Texas Medical Branch in Galveston in the April Pediatric Research. Inflammation is one way the body fights infection. But sometimes the body fights too aggressively, and healthy tissue succumbs. Indeed, one reason gastrointestinal disease can be so devastating to infants is that the inflammatory process tends to get carried away.

At the meeting, Garofalo described preliminary data suggesting that newborns do not produce IL-10 as effectively as adults. He says that may help explain the significance of another of their findings: that colostrum, the fluid that precedes breast milk, contains the most IL-10.

The emerging picture indicates that mom's milk offers a host of beneficial chemicals that probably work in concert with antibodies to protect babies from life-threatening infections.