COS cells

COS is a fibroblast-like cell line 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 word COS is an acronym, derived from the cells being CV-1 (simian) in Origin, and carrying the SV40 genetic material. Two forms of COS cell lines commonly used are COS-1 and COS-7.

Applications
The COS cell line is often used by biologists when studying the monkey virus SV40. Cells from this line are also often transfected to produce recombinant proteins for molecular biology, biochemistry, and cell biology experiments.

When an expression construct with an SV40 promoter is introduced into COS cells, the vector can be replicated substantially by the large T antigen.