WI-38 is a diploid human cell culture line composed of fibroblasts derived from lung tissue of a 3 months gestation female fetus. The cell line, isolated by Leonard Hayflick and Paul Moorhead in the 1960s, has been used extensively in scientific research, with applications ranging from developing important theories in molecular biology to the production of many types of vaccines. The contributions from this cell line on research has been credited with saving the lives of "millions of people".
The WI-38 cell line stemmed from earlier work with growing cell cultures done by Hayflick and Moorhead. Observations of similar cell lines led to the discovery that cells would gradually experience signs of senescence as they divided, first slowing and then stopping division altogether. This finding would later be known as the Hayflick limit, which indicated that normal human cells could only undergo a limited number of divisions, and later contributed to the discovery of the biological roles of telomeres. However, during this period of research, the team also discovered that if cells were properly stored in a freezer, cells would remain viable and could provide enormous numbers of cells for research purposes. Based on this, Hayflick was given another line of fetal cells to try to preserve and duplicate using this method. This cell line became WI-38.
WI-38 was invaluable to early researchers, especially those studying virology and immunology, since it was a readily-available cell line of normal human tissue, unlike the HeLa line, which were cancerous cells. Researchers in labs across the globe have since used WI-38 in their discoveries, most notably in the development of vaccines. Over a billion vaccine doses worldwide can be traced to work done on WI-38, covering conditions including measles and rubella.
WI-38 cells are used to produce several vaccines including Adenovirus, MMR and Varicella zoster. Infected WI-38 cells secrete the virus, and can be cultured in large volumes suitable for commercial production.