Human Fetuses Respond to Mother's Flu Immunization

Contrary to the stereotypical view, in which the fetal immune system is considered at best wimpy, allergy researchers at Columbia University found about a third of babies of vaccinated mothers were born with cells ready to combat the flu virus. "This indicates that the baby's got a pretty well-developed immune system by the time it's born."

The understanding of the fetal immune system seems to have been flawed due to the difficulty in detecting T cells targeted against a specific antigen, and possibly because previous work used techniques criticized for their lack of specificity. The researchers at Columbia were able to solve this problem by using a fluorescent molecule that mimics the antigen, and lights up when the appropriate immune cell sticks to it. A follow-up screening of the umbilical-cord blood from babies born to women who had been vaccinated against the flu during their second or third trimester found the sought antibodies and T cells in about one out of every three babies.