WI-38 is a diploid human cell line composed of fibroblasts derived from lung tissue of a 3-month-gestation female fetus.The fetus came from the elective abortion of a Swedish woman in 1962, and was used without her knowledge or permission. The cell line was isolated by Leonard Hayflick the same year, and has been used extensively in scientific research, with applications ranging from developing important theories in molecular biology and aging to the production of most human virus vaccines.