The phrase "immortal cells" refers to cells that have the ability to divide and replicate indefinitely, without facing natural cell aging or death. These cells can keep growing and multiplying without limit. Full definition
In mouse they are defined functionally as a karyotypically normal immortal cell line that can give rise to all the future lineages of the conceptus [3]. (journals.plos.org)
Amounts of telomerase RNA increased in immortal cells derived from primary mouse fibroblasts. (science.sciencemag.org)
To allay that fear, Shay and his colleagues checked the newly immortal cells for other telltale traits of cancer cells. (sciencemag.org)