“Feeding the Baby”-Serum and Other Supplements to Chemically Defined Medium1

Abstract

The widespread use of mammalian cell culture has exceeded development of new and improved methods, and has led to the erroneous impression that the current state of the art represents its final and perfected form, l.e., a scientific fait accompli. The use of serum as a supplement for chemically defined tissue-culture medium is an expedient but biologically unsatisfactory practice. Serum is a source of chemical and experimental variability in vitro and can introduce adventitious microbial contaminants. Serum is not an absolute in vitro requirement, since several primary cell strains and long-term cell lines can be grown continuously in serum-free culture medium. Large volumes of high-quality sera are becoming increasingly difficult and expensive to obtain. The need for serum, its proposed functions, and prospects for the development of biologically adequate alternatives are considered.