Fig. 4.

Blocking endogenous TNF sustains IFN-α release from pDCs exposed to influenza virus. pDCs were generated and purified as described in Fig. 3 and cultured with influenza virus. (a) Primary cultures were carried out in the presence or absence of isotype control or TNF-neutralizing mAb. Supernatants were harvested at 24 h after centrifugation of culture plates, and IFN-α release (y axis) was measured by ELISA. (b) Cell pellets were resuspended in fresh medium (without mAbs), influenza virus was added, and cultures were carried out for an additional 24 h. Supernatants from secondary cultures were analyzed by ELISA (y axis). (c) Flow cytometry analysis of HLA-DR expression by pDCs cultured for 24 h with influenza virus with or without TNF-neutralizing mAb (Right). Fluorescence intensity is shown on the x axis. Data are representative of three experiments.