Effect of addition of rIL-2 or rIL-4 on tumor cell proliferation. Tumor cell lines, LSA, PE-3T, EL-4, and P815 were cultured in the presence of 50 U (50 u) of rIL-2 or rIL-4 for 24 (A) or 48 (B) hours. Cells incubated with media alone were used as a control. The cell proliferation was measured by counting the viable cells using trypan-blue dye exclusion. Means of cell numbers from experimental groups and the control SEM were plotted. Statistically significant differences (P < .05) from the control values have been indicated with an asterisk.