Critical adjustment of cysteine and glutamine concentrations for improved clonal growth of WI-38 cells.

Clonal growth of WI-38 cells with a plating efficiency of 45% has been achieved in a synthetic nutrient mixture (MCDB 102) supplemented with either whole or dialyzed fetal bovine serum precisely. Deviation by a factor of three in either direction from the optimum concentration (9.0 x 10(-5) M) eliminates essentially all clonal growth. A high concentration of glutamine (2.5 x 10(-3) M) is also needed for optimum clonal growth.