Assembly Line for Immune Model T's?

During its teenage years, the human body permanently shuts down production of T cells--a crucial immune defender against infection--like a country shutting down an ammunition factory during a war. Although the T cells created in childhood continue to work, their numbers decline. Now researchers may have found a way to get an alternate T-cell assembly line cranked up in adulthood, says a report in tomorrow's issue of Nature.

Most people create enough T cells during childhood to last a lifetime. But HIV and cancer radiation treatments can reduce the size of the body's precious T-cell inventory, crippling the immune system. "If you can boost the number of T cells, you can extend these people's lives," says Christopher Clegg, an immunologist at Bristol-Myers Squibb Pharmaceuticals in Seattle.

Clegg's team may have stumbled upon a way to do just that. In one experiment, they introduced into normal mice a cow gene that codes for oncostatin M, a protein involved in T-cell production. To their surprise, several weeks later they found that the mouse lymph nodes--which normally only store mature T cells--held what appeared to be immature T cells usually seen only in the thymus. The researchers also showed that these lymph-node cells matured into T cells that successfully fended off tumors implanted in the mice.

Experts are greeting the report with cautious enthusiasm. The data showing production of immature T cells are "very convincing," says Jonathan Sprent, an immunologist at Scripps Research Institution in La Jolla, California. But, he says, "the evidence that they differentiate into mature T cells is not as clear."

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