ThymusWords
Two Thymuses Are Better Than One
By Meagan White
ScienceNOW Daily News
2 March 2006
Mice have a trick up their sleeve--or rather in their neck: a second thymus. The original thymus, nestled under the breastbone, churns out infection-fighting T cells. Now scientists have found that, at least in mice, this additional thymus has the same function. The finding raises the prospect of a confounding factor in immunological studies in mice, and perhaps humans.
In the early 1960s, Jacques Miller, the so-called "father of the thymus," noticed that when he removed the multilobed organ from mouse chests, the animals retained some of their immune functions. This suggested to him that mice had thymus tissue elsewhere in their bodies. Just a few years later, Lloyd Law and colleagues at the National Institutes of Health in Bethesda, Maryland, proved Miller right, finding an extra, single-lobed thymus concealed below cervical muscles in the lower necks of mice. No one bothered to see whether this extra thymus actually worked, however, because scientists believed it was too small to have any immune benefits.
Now, immunologist Hans-Reimer Rodewald and his colleagues at the University of Ulm in Germany, have discovered that in certain strains of mice, the second thymus is as good as the first. While studying immune disorders in BALB/c mice, a strain deficient in T cell production, the researchers stumbled across the cervical thymus. To prove that this structure was indeed an extra thymus, the team genetically modified the mice to express fluorescent molecules in thymus tissue. Sure enough, the spare thymus lit up.
But did it work? Rodewald's team decided to graft the spare thymus into immunodeficient mice. When the researchers inoculated the rodents with hepatitis B particles, the mice mounted the same type and strength of immune response seen in healthy animals. That means a second thymus organ could contribute to the health of a mouse in other experimental settings, such as after surgery that removes the thymus, the team reports online today in Science. And that may explain why, in some studies, researchers have continued to find T cells in mice, even after the thymus had been excised, says Rodewald.
Cervical thymus tissue has been observed in some humans as well, but scientists had assumed that this too had no function. Daniel Littman, immunologist at New York University School of Medicine, speculates that it might: "During cardiac surgery in children, the thymus is often removed, and yet there is no known detrimental effect on the immune system," he says. "This is obviously something that will need to be evaluated."
.MGW.
By Meagan White
ScienceNOW Daily News
2 March 2006
Mice have a trick up their sleeve--or rather in their neck: a second thymus. The original thymus, nestled under the breastbone, churns out infection-fighting T cells. Now scientists have found that, at least in mice, this additional thymus has the same function. The finding raises the prospect of a confounding factor in immunological studies in mice, and perhaps humans.
In the early 1960s, Jacques Miller, the so-called "father of the thymus," noticed that when he removed the multilobed organ from mouse chests, the animals retained some of their immune functions. This suggested to him that mice had thymus tissue elsewhere in their bodies. Just a few years later, Lloyd Law and colleagues at the National Institutes of Health in Bethesda, Maryland, proved Miller right, finding an extra, single-lobed thymus concealed below cervical muscles in the lower necks of mice. No one bothered to see whether this extra thymus actually worked, however, because scientists believed it was too small to have any immune benefits.
Now, immunologist Hans-Reimer Rodewald and his colleagues at the University of Ulm in Germany, have discovered that in certain strains of mice, the second thymus is as good as the first. While studying immune disorders in BALB/c mice, a strain deficient in T cell production, the researchers stumbled across the cervical thymus. To prove that this structure was indeed an extra thymus, the team genetically modified the mice to express fluorescent molecules in thymus tissue. Sure enough, the spare thymus lit up.
But did it work? Rodewald's team decided to graft the spare thymus into immunodeficient mice. When the researchers inoculated the rodents with hepatitis B particles, the mice mounted the same type and strength of immune response seen in healthy animals. That means a second thymus organ could contribute to the health of a mouse in other experimental settings, such as after surgery that removes the thymus, the team reports online today in Science. And that may explain why, in some studies, researchers have continued to find T cells in mice, even after the thymus had been excised, says Rodewald.
Cervical thymus tissue has been observed in some humans as well, but scientists had assumed that this too had no function. Daniel Littman, immunologist at New York University School of Medicine, speculates that it might: "During cardiac surgery in children, the thymus is often removed, and yet there is no known detrimental effect on the immune system," he says. "This is obviously something that will need to be evaluated."
.MGW.
posted by Meagan G at
7:31 PM
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