Characterization of a new cell line, XL2, obtained from Xenopus laevis and determination of optimal culture conditions.

A new amphibian permanent cell line is described. It is called XL2 and was initiated from Stage 35 tadpoles of Xenopus laevis. The cell line has an epithelioid morphology and most cells can be classified into two populations with respective chromosome modal numbers 36 and 74. Contact inhibition is low. Its growth is vigorous in L15 or MEM medium supplemented with fetal bovine serum. The mean doubling time is 39 hr and the saturation density is 700,000 cells/cm2 at 25 degrees C. The absolute plating efficiency is about 70%. Cell line XL2 is unable to grow in L15 medium containing a macromolecular fraction of fetal bovine serum. Growth is restored if the latter medium is supplemented with 10 micrograms/ml of hypoxanthine. Optimal conditions for the dye exclusion test, for harvesting the cells, and for cloning in petri dishes are described.