Objective To establish a method for detection of duck interferon - gamma (DuIFN - γ) bioactivity in vitro. Methods One of the biological properties of IFN - γ is the ability of activating macrophage in vitro to generate nitric oxide (NO). To detect the duck interferon - gamma (DuIFN -γy) activity

we utilised duck peripheral blood mononuclear cells (PBMCs) and Sephadex G - 100 induced peritoneal exudate cells (PECs) as target cells to monitor the change of NO level of the target cells before or after stimulation of LPS

PHA of L - arginine. Results The results indicated that a limited increase of NO concentration following LPS or L - arginine stimulation was observed in chicken PBMCs

but not in duck PBMCs. The possible reason is assumed to be related to the differential distribution of macrophages in PBMCS from different species. Following stimulation with LPS or P~

the duck PECs with a high cell density produced a remarkable increase of NO concentration compared to the group with a low cell density. Conclusion Duck PEGs with high cell density are sensitive to the stimulation of LPS or P~

which can be used as a method to detect the activity of duck IFN - γ.