Temperature influences on different human alpha interferon activities

Influences of different incubation temperatures within the physiological range on three different biological activities of human leukocyte-derived alpha interferon (IFN) (the antiviral effect, the antiproliferative activity, and the augmentation of natural killer cell (NK) activity) were investigated in vitro. Using the plaque-reduction assay (U cells challenged with VSV), the antiviral activity by IFN was found to be lower at 35 degrees C and higher at 38 degrees C and 39 degrees C than at 37 degrees C. Using the CPE (cytopathogenic effect) inhibition technique (Vero cells challenged with VSV), the antiviral activity was slightly enhanced at 38 degrees C, 39 degrees C, and 40 degrees C, respectively, when compared with 37 degrees C. The antiproliferative activity on Daudi cells and G-361 melanoma cells was enhanced at elevated temperatures. On the other hand, the antiproliferative activity on PLC/PRF/5 hepatoma cells was lower at 38 degrees C and 39 degrees C than at 37 degrees C, but higher at 40 degrees C. NK activity of PBL after 2 h incubation at 41 degrees C was remarkably lower than that at 37 degrees C, while it was not affected by 2 h incubation at 35 degrees C and 39 degrees C, respectively. When PBL was treated with IFN for 2 h at the temperatures described above, NK activity was equally augmented at all temperatures tested. Our results suggest that elevated incubation temperature potentiates the antiviral and the antiproliferative activities, but does not affect the NK augmenting activity of HuIFN-alpha (Le).