COS cells

COS is a cell line often used by biologists when studying the monkey virus SV40. It is also often used to transfect cells to produce recombinant proteins for molecular biology, biochemistry, and cell biology experiments. Two forms of COS cell lines commonly used are COS-1 and COS-7.

The COS cell line was obtained by immortalizing a cell line derived from kidney cells of the African green monkey with a version of the SV40 genome that can produce large T antigen but has a defect in genomic replication.

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

The word COS is derived from Cercopithecus aethiops.