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 contains receptors that can identify peptides and mount
an immune system response, if appropriate. T cells that attack
foreign entities in the immune system roam the body looking for
these peptides.
Peptides
contain information about cell health and are often the first
notice the immune system receives about a disease attacking the
body. Peptides are brought to the surface of the cell by MHC molecules
that continually sample a cell for disease.
National
Jewish Medical and Research Center is the number one hospital
in the United States for respiratory disease treatment, U.S. News
& World Report, 1998-2000.
This
article has been adapted from a news release on what T cells “see”
in a normal thymus that controls the development of immune-system
aggressive T cells that was issued by National Jewish Medical
And Research Center, www.nationaljewish.org.
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