The ambient temperature at which mice are housed is generally an overlooked parameter, yet it can have a substantial influence on a wide range of experimental results. In the Proceedings of the National Academy of Sciences, Repasky and colleagues demonstrate how antitumor responses can vary according to whether mice are maintained at conventional housing temperatures (22–23 °C) or mouse 'thermoneutral' temperatures (30–31 °C). Mice kept under thermoneutral conditions have less tumor growth and metastasis in various standard models. The use of either immunodeficient hosts or depletion of cytotoxic T cells abolishes any temperature-dependent differences in tumor growth. Furthermore, under thermoneutral conditions, mice have a greater abundance of cytotoxic T cells, with more activation and interferon-γ production, as well as fewer Treg cells in the tumor mass. Ambient temperature, therefore, has a considerable effect on antitumor functionality in mice, and the standard housing conditions in which mice are maintained triggers cold stress and may impair such responses.

Proc. Natl. Acad. Sci. USA 110, 20176–20181 (2013)