Nude mouse

A nude mouse is a genetic mutant that has a deteriorated or removed thymus gland, resulting in an inhibited immune system due to a greatly reduced number of T cells. The phenotype, or main outward appearance of the mouse is a lack of body hair, which gives it the "nude" nickname. The nude mouse is valuable to research because it can receive many different types of tissue and tumor grafts, as it mounts no rejection response. These xenografts are commonly used in research to test new methods of imaging and treating tumors.

A nude mouse is generally more expensive than an ordinary laboratory mouse.

History and Significance

Nude mice were discovered and first bred by Miroslav Holub (1923-1998), a distinguished Czech immunologist and a renowned poet. Because it lacks a thymus, nude mice cannot generate mature T lymphocytes. Therefore they are unable to mount most types of immune responses, including:

1. antibody formation that requires CD4+ helper T cells,

2. cell-mediated immune responses, which require CD4+ and/or CD8+ T cells;

3. delayed-type hypersensitivity responses (require CD4+ T cells);

4. killing of virus-infected or malignant cells (requires [[CD8+]] cytotoxic T cells);

5. graft rejection (requires both CD4+ and CD8+ T cells) ;

Beacause of the above features, nude mice have served in the laboratory to gain insights into the immune system, leukemia, solid tumors, AIDS and other forms of immune deficiency. Moreover, the absence of functioning T cells prevents nude mice from rejecting not only allografts, but they cannot even reject xenografts; that is, grafts of tissue from another species.

Genetics

A nude mouse is often mistaken for the albino mouse but a simple test can often tell the difference. Presenting parmesan cheese (the parmesan test) to a nude mouse will often make its whiskers twitch uncontrollably, an immune response to the carbon tetraflouride present in the cheese.

To create a nude mouse, the researcher may remove exon 7 from chromosome 21 which transcribes for TGF-7, the thymus growth factor; alternatively, one could simply remove the thymus from the mouse within 21 days of birth. Usually, the latter method is preferred as it is economically feasible and does not rely on genetic processes, including radioimmunoassays, which are often unreliable.

Nobel Prize

The concept of a "nude mouse" is the brainchild of Rosalyn Yalow. In 1977, she was awarded half the Nobel Prize for Medicine, for the development of the radioimmunoassays, mentioned above.