THURSDAY, March 2 (HealthDay News) -- Researchers have unexpectedly discovered that mice contain a second thymus located in the neck that appears to be fully functional in producing normal T cells, according to a study published online March 2 in Science.
Hans-Reimer Rodewald, Ph.D., of the University of Ulm in Germany, and colleagues investigated several structures with lymphoid characteristics that they found in the ventral necks of mice.
The researchers found that the structures displayed the hallmarks of thymus structure but were not identical to the chest thymus, containing only a single lobe and fewer thymocytes, of which a greater percentage were mature. The presence of the second thymus varied depending on the mouse strain, with 90 percent of one strain containing a cervical thymus compared with only 50 percent of another strain. Next, the researchers transplanted a cervical thymus into mice lacking a thymus and found that the new thymus could be colonized with T cells from the host and produce T cells that appeared functionally normal.
"The identification of a regular second thymus in the mouse may provide 'evolutionary links' to thymus organogenesis in other vertebrates, and suggests a need to reconsider the effect on thoracic thymectomy on de novo T-cell production," Rodewald and colleagues conclude.
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