June 29 (Bloomberg)—Injections of embryonic stem cells, versatile building blocks that can take on many functions, can reconstitute aging immune systems, according to a study of cows appearing today in the journal Cloning and Stem Cells.

Stem-cell injections replaced the immune systems of two older cows that lived 400 days afterwards without complications, said study leader Robert Lanza, medical director of ACT Holdings Inc., a Worcester, Massachusetts, biotechnology company.

Using a technique similar to one South Korean researchers have experimented with in humans, Lanza cloned cow embryos by putting DNA from a cow’s skin cell in the animal’s egg cell to grow an embryo. It will probably be at least five years before such therapies are suitable for use in people, Lanza added.

“Think of an elderly person who’s susceptible to pneumonia,” he said. “With a simple injection, you could give them new, useful cells.”

The study demonstrates how tissues genetically matched to a DNA donor might be used to treat patients with immune disorders, said Piero Anversa, a stem-cell researcher and director of the Cardiovascular Research Institute at New York Medical College.

“This is a very impressive study,” Anversa said in an interview. “There is no precedent to what has been done in this paper.”

Replacement Cells

Stem cells are genetically programmed to grow new tissues and replace damaged cells. Researchers consider embryonic stem cells the most powerful type because they can create the widest variety of cells.

People with injured immune systems, such as those with HIV, the virus that causes AIDS, are at high risk of infection with bacteria and viruses. Lanza designed the study to see whether he could replace the immune system in older, weaker cows without eliminating their existing immune cells.

“We thought the cells might be competitive enough to make room in the immune system on their own,” he said in a telephone interview. “If you were doing this in people, you wouldn’t want to kill off all the immune cells in an AIDS patient if you didn’t have to.”

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