[OT] Flu-Fighting Fetuses

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Flu-Fighting Fetuses

By Adam Hinterthuer

ScienceNOW Daily News

1 June 2007

Via the placenta, a newborn baby receives a 6-month supply of antibodies from

its mother, arming it against a world chock-full of allergy-causing particles

and viruses. But it turns out that the baby may have been preparing its immune

system for battle well before birth. New research indicates that developing

fetuses are able to mount their own specific immune response to flu vaccines

received by their mother. The findings could help end a debate over just how

complex a fetus's immune system is.

A fetus contains many kinds of immune cells, yet most immunologists believe

those cells are too immature to target specific allergy-causing molecules, or

antigens. That's because no antigen-specific antibodies had ever been found in

umbilical cord blood. Instead, immunologists assumed that a fetus could only

launch general attacks on infections, while relying on the mother's immune

system for antigen-specific responses. But , an allergist and

immunologist at Columbia University, believed the fetal immune system was more

advanced than researchers were giving it credit for.

and colleagues studied a group of 126 women who received a flu vaccine

during pregnancy. When those women gave birth, the researchers took samples of

each newborn's cord blood. They collected 70 usable samples and used a technique

that had never been applied to cord blood to look at the immune response at the

cellular level. That way they could identify, cell by cell, whether a fetus had

produced specific antibodies in response to the flu vaccine. They found that 40%

of the samples contained antigen-specific T and B immune cells and antibodies.

says it's unclear why only some of the fetuses exhibited an immune

response, but she says what's significant is that the flu-specific antibodies

were there at all. Some were IgM antibodies, which are too large to pass through

the placenta from mother to child, meaning they were undoubtedly produced by the

fetus. Far from being defenseless, the fetal immune system is quite capable of

responding to infection, the team reports today in the Journal of Clinical

Investigation.

The results help confirm the long-contentious theory that fetuses can mount

specific immune responses, and they are " a real bonus " to the field, says Aimen

Shaaban, an immunologist at the University of Wisconsin, Madison. Still, he

notes that the vaccinations were given in the third trimester, by which point

the fetal immune system may have had time to become more complex. If the work is

repeated, Shaaban says, it would be good to look at fetuses in earlier

trimesters to get a better idea of when, exactly, these advanced immune system

responses begin to kick in.

http://sciencenow.sciencemag.org/cgi/content/full/2007/601/2?etoc