Effect of IL-9 on VEGF production in KU812 and HMC-1 cells.

KU812 and HMC-1 cells were inoculated with Dengue virus-2 (DV) or UV-irradiated Dengue virus-2 (UDV) in the presence or absence of IL-9 (200 ng/ml), and VEGF levels were then examined. VEGF production by KU812 and HMC-1 cells was significantly increased in the presence of IL-9 when the cells were cultured with DV and human Dengue virus-immune serum (1∶1000 final dilution). However, significant VEGF production was not observed in cells when KU812 and HMC-1 cells were infected with DV or UDV in the presence of normal human serum (1∶1000 final dilution) and IL-9 (data not shown). Significant VEGF production was not observed when KU812 and HMC-1 cells were infected with DV alone (data not shown).IL-9+ in KU812 *pa: C3/36 medium alone (mock infection) served as a negative control.b: Activation of mast cells with C48/80 (300 µg/ml) was used as a positive control.*p