This cell line was developed by the Institute for Medical Research from the lung and skin tissue of an aborted Caucasian baby boy in the US, 3 months gestation, in 1983. The designation stands for Institute for Medical Research, cell strain 91. His cells were intended to replace MRC-5.
The culture was established from a human male fetus obtained after a therapeutic abortion performed by hysterectomy at the time of sterilization on a 41-yr-old white female (para 6, gravida 7).The gestational age of the fetus was approximately12 wk; its shoulder-rump length was 7 cm and there were no apparent physical abnormalities. The mother’s medical history was unremarkable with the exception of bronchial asthma for many years, for which she took medication regularly. She was also a one pack-a-day cigarette smoker.
 That is, this was her 7th pregnancy (gravida 7), and she had given birth to 6 children (para 6) already.
 W. Nichols et al., “Characterization of a new human diploid cell line: IMR-91,” In Vitro Vol 19:10 (1983), pp. 797-804. < https://link.springer.com/article/10.1007/BF02618099>
“Resources Available for Conducting Research on Aging,” National Institute on Aging (1993). <https://cogforlife.org/wp-content/uploads/Resources-Available-for-Conducting-Research-on-Aging.pdf>