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J. Exp. Med.,
Volume 189, Number 2, January 18, 1999 331-339
By


From the * Institut de Génétique et de Biologie Moléculaire et Cellulaire (CNRS/INSERM/ULP),
Strasbourg, 67404 Illkirch Cedex, France; and the Little is known about the events triggering lymphocyte invasion of the pancreatic islets in prelude to autoimmune diabetes. For example, where islet-reactive T cells first encounter antigen has not been identified. We addressed this issue using BDC2.5 T cell receptor transgenic mice,
which express a receptor recognizing a natural islet beta cell antigen. In BDC2.5 animals, activated T cells were found only in the islets and the lymph nodes draining them, and there was a
close temporal correlation between lymph node T cell activation and islet infiltration. When
naive BDC2.5 T cells were transferred into nontransgenic recipients, proliferating cells were
observed only in pancreatic lymph nodes, and this occurred significantly before insulitis was
detectable. Surprisingly, proliferation was not seen in 10-day-old recipients. This age-dependent dichotomy was reproduced in a second transfer system based on an unrelated antigen artificially expressed on beta cells. We conclude that beta cell antigens are transported specifically
to pancreatic lymph nodes, where they trigger reactive T cells to invade the islets. Systemic or
extrapancreatic T cell priming, indicative of activation via molecular mimicry or superantigens,
was not seen. Compromised presentation of beta cell antigens in the pancreatic lymph nodes of
juvenile animals may be the root of a first "checkpoint" in diabetes progression.
Walter and Eliza Hall Institute for Medical
Research, Melbourne, Victoria 3050, Australia
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