Feeder cells are usually adherent growth-arrested cells that are viable and bioactive and serve as a substratum, secreting factors into the medium or on their surface, on which other cells are grown. Feeder layer cells are treated with irradiation or other treatments such as mitomycin-C that cause them to cease proliferating. Some cells require contact with feeder cells, while others can be grown in feeder-free conditions.
Mouse embryonic fibroblasts (MEFs) are commonly used as a feeder layer for stem cell culture. Feeder layers of human origin include human foreskin fibroblasts, human dermal fibroblasts and amniotic mesenchymal.