A new method of permanently marking T cells has allowed Emory University immunologists and colleagues to overcome one of the most challenging barriers to understanding just how the immune system works. The discovery, which could have far-reaching implications for vaccine development, transplantation and treatment of auto-immune diseases, is reported in the June 10 issue of Nature.

For the first time, scientists are now able to visually distinguish which T lymphocytes become memory cells -- those with the ability to vigorously attack previously encountered pathogens for years after an organism is exposed, either through infection or immunization.

Joshy Jacob, Ph.D., assistant professor of microbiology and immunology at Emory University School of Medicine and nobel laureate David Baltimore, Ph.D., president of the California Institute of Technology, developed the method of irreversibly tagging T lymphocytes with a cell surface protein in genetically engineered mice. The protein, which Jacob calls a "reporter gene," is found in the human placenta but not in mice. "In these mice we can, for the first time, visualize memory T cells, follow their fate in vivo and study their normal physiology in health, autoimmune disease and organ transplantation," says Jacob.

Although the existence of immune memory has been recognized and documented for more than 2,000 years, Dr. Jacob says, research has lagged behind because scientists could not unequivocally identify memory lymphocytes. Until now, there have been no known cell surface markers to distinguish between memory and non-memory (naïve) lymphocytes. The ability to remember and respond to invading organisms -- even years later -- is one of the fundamental features of the immune system. Acute viral infections induce two types of long-term memory -- humoral memory in which B cells produce antibodies to prevent infection by viruses, and cellular immunity, in which T cells activated by specific vir
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Contact: Holly Korschun
hkorsch@emory.edu
404-727-3990
Emory University Health Sciences Center
9-Jun-1999