Permanent cell

Permanent cells are cells that are incapable of regeneration. These cells are considered to be terminally differentiated and non proliferative in postnatal life. This includes brain cells, neurons, heart cells, skeletal muscle cells and RBCs.

Disease and virology studies can use permanent cells to maintain cell count and accurately quantify the effects of vaccines. Some embryology studies also use permanent cells to avoid harvesting embryonic cells from pregnant animals; since the cells are permanent, they may be harvested at a later age when an animal is fully developed.

...
Wikipedia