Production of Interferon-γ by Chicken T Cells

Abstract

In mammals, interferon (IFN)-α/β (type I) is typically resistant to exposure to heat and low pH, whereas IFN-γ (type II) is labile. Type I IFN has been described in birds; however, the existence of type II IFN has been questioned. We have generated cloned chicken T cell lines that produce high levels of IFN and have studied the physiochemical properties of this IFN activity to determine whether it represents the type I or type II IFN found in mammals. When incubated at 60°C, the IFN activity present in the supernatants from these chicken T cells was found to be labile, two-thirds of the activity being lost within 1–2 minutes. Consistent with IFN-γ activity, this heat-labile IFN was also sensitive to exposure to pH 2. The heat-resistant IFN lost activity at a much slower rate (half-life >2 h at 60°C) and was also resistant to exposure to pH 2, which is characteristic of IFN-α/β. To confirm further the presence of IFN-γ activity, these T cell supernatants were assayed for their ability to activate macrophages as measured by induction of nitrite production. Consistent with mammalian IFN-γ, the nitrite-inducing activity was found to be heat labile, with over 90% of the activity lost within 5 minutes of heating. These results show that chicken T cells produce IFN-γ.