T Cell Training Enhances Immune System Diversity

A recent study described the role of the major histocompatability complex (MHC) system in the training and activation of immune T cells. The study was published in the November 29, 2002, issue of Science.

Investigators from the Oregon Health and Science University (Beaverton, USA) used mice infected with herpes simplex virus to evaluate the quality of the T cell response against the virus. They concentrated on molecules of the major histocompatability complex (MHC) system exposed on the surface of infected cells and alert T cells.

"The MHC molecules have two roles. First, they act like the traffic cops in the body. They look for invaders and, once they find them, they call in T cells to defeat a pathogen,” explained senior author Dr. Janko Nikolich-Zugich, a senior scientist at the Oregon Health and Science University Vaccine and Gene Therapy Institute. "But, just as importantly, they also ‘train' T cells when the pathogen is not around. They do this by selecting and expanding only those T cells that can be appropriately directed to find and destroy a pathogen when it attacks.”

By providing ‘training' to a wide, diverse set of T cells, some MHC molecules can ensure that the pathogen will be met by the very best T cells, able to kill the pathogen promptly at the beginning of infection. The more diverse set of T cells an animal has, the better chance the cells have of detecting a pathogen early and successfully fighting it off. The fact that as people age their T cell diversity drops helps explain why seniors are more susceptible to the flu and other diseases than the rest of the population

"This research is of particular interest to populations that are highly vulnerable to disease, such as the aging population,” said Dr. Nikolich-Zugich. "We hope that years down the road, this research finding will help us boost the immune systems of the elderly.”



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