Down's syndrome: karyotypic stability of trisomy 21 in an established lympho-blastoid cell line.

A trisomic lymphoblastoid cell line derived from the peripheral blood of a patient with Down's syndrome was sequentially analyzed for chromosome constitution for 16.5 months of continuous culture in vitro. The cell line was found to maintain a modal chromosome number of 47 with trisomy 21. Parallel studies of modal chromosomes before and after banding procedures revealed no structural abnormalities except trisomy 21.