DENVER-Researchers at National Jewish Medical and Research Center have identified what T cells 'see' in a normal thymus that controls the development of functional or immune-system aggressive T cells, according to today's issue of the journal Immunity.

"This is the first time anybody has described what T cells really 'see' when they are positively selected in the thymus," said Uwe Staerz, M.D., Ph.D., a National Jewish researcher who studies the immune system.

This research helps expand the understanding of how the immune system develops. In the future, this research may help people who have cancer, because those with cancer don't have fully functional immune systems. Understanding T cell development is necessary to comprehend the development of autoimmune diseases like cancer.

In the thymus, the major histocompatability complex molecule (MHC) acts as a 'filter' for new T cells. Although scientists have long known that the thymus was the screening location for T cells, Dr. Staerz and a team of researchers were able to identify the specific peptide located on the MHC that positively selects T cells. A peptide called ND1, located on MHC in the thymus, was found to positively select T cells that later fight disease in the body. It's this peptide that the T cell 'sees' in the thymus.

The thymus, a small organ located in the lower neck, helps facilitate the normal development of the immune system early in life. The thymus acts as a 'filter' that selects T cells with working receptors, which later sample peptides on the surface of cells. Most of the T cells that don't have the correct receptors and can potentially attack the immune system are screened by the thymus and then destroy themselves. However, some T cells, which later may cause an autoimmune disease, pass throught the thymus because not all antigens that can be seen by T cells are present in this organ.

A positively selected T cell is allowed to pass through the thymus because it
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Contact: Jordan Gruener
gruenerj@njc.org
303-398-1002
National Jewish Medical and Research Center
22-Jul-1999