Reporting in the Aug. 25 issue of Nature, researchers at The University of Texas M. D. Anderson Cancer Center found that Hassall's corpuscles produce chemical signals that instruct dendritic cells in the thymus to induce development of these regulatory T cells - the critically important immune system cells that patrol the body looking for "bad' T cells that can produce autoimmune disease.
"These mysterious little structures in the thymus are responsible for producing the T cell policemen that our bodies depend so heavily on," says the study's lead author, Yong-Jun Liu, M.D., Ph.D., professor and chair of the Department of Immunology. "It is a very smart system that evolved during evolution to efficiently keep the immune system in check."
The thymus functions like a school to educate immature immune system "T" (for thymus) cells. T cells are white blood cells that play vital roles in the immune system, including the identification of specific foreign "antigens" in the body (toxins, bacteria, viruses and other invading cells) and the activation and deactivation of other immune cells.
A chief function of the thymus is the selection of the T cell repertoire the immune system uses to combat infections - a process known as "clonal selection theory" that earned the researchers who discovered it a Nobel Prize in 1960. This involves the "positive selection" of T cells that are non self-reactive and the elimination, through "negative selection," of T cells that are self-reactive or autoreactive. If allowed outside of the thymus gland, these autoreactive T cells would produce a harmful immune response against the body's own tissues, so the immune system flags "
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Contact: Nancy Jensen
nwjensen@mdanderson.org
713-792-0655
University of Texas M. D. Anderson Cancer Center
11-Oct-2005