Interleukin 13 (IL13) is cytokine secreted by many cell types, but especially T helper type 2 (Th2) cells. IL13 has effects on immune cells that are similar to those of the closely related cytokine IL4. In addition, IL-13-bound IL-13 Rα2 can directly promote tumor cell proliferation、invasiveness and the development of tissue fibrosis. To test the effect of IL13 on cell proliferation, TF-1 cells were seeded into triplicate wells of 96-well plates and allowed to attach, replaced with various concentrations of recombinant human IL13. After incubated for 72h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10 μl of CCK-8 solution was added to each well of the plate, then the absorbance at 450 nm was measured using a microplate reader after incubating the plate for 1-4 hours at 37 ℃. Cell viability was assessed by CCK-8 assay after incubation with recombinant human IL13 for 72h. The result was shown in Figure 1. It was obvious that IL13 significantly increased cell viability of TF-1 cells. The ED50 of recombinant human IL13 is 0.914 μg/ml.