COS cells

COS are fibroblast-like cell lines derived from monkey kidney tissue. COS cells are obtained by immortalizing CV-1 cells with a version of the SV40 virus that can produce large T antigen but has a defect in genomic replication. The CV-1 cell line in turn was derived from the kidney of the African green monkey.

The acronym "COS" is derived from the cells being CV-1 (simian) in Origin, and carrying the SV40 genetic material. Three COS lines were created (COS-1, COS-3 and COS-7), of which two are commonly used (COS-1 and COS-7).