PRODUCTION OF INTERFERON-GAMMA BY CHICKEN T-CELLS

In mammals, interferon (IFN)-alpha/beta (type I) is typically resistan t to exposure to heat and low pH, whereas IFN-gamma (type II) is labil e, Type I IFN has been described in birds; however, the existence of t ype II IFN has been questioned, We have generated cloned chicken T cel l lines that produce high levels of IFN and have studied the physioche mical properties of this IFN activity to determine whether it represen ts the type I or type II IFN found in mammals, When incubated at 60 de grees C, the IFN activity present in the supernatants from these chick en T cells was found to be labile, two-thirds of the activity being lo st within 1-2 minutes, Consistent with IFN-gamma activity, this heat-l abile IFN was also sensitive to exposure to pH 2, The heat-resistant I FN lost activity at a much slower rate (half-life >2 h at 60 degrees C ) and was also resistant to exposure to pH 2, which is characteristic of IFN-gamma. To confirm further the presence of IFN-gamma activity, t hese T cell supernatants were assayed for their ability to activate ma crophages as measured by induction of nitrite production, Consistent w ith mammalian IFN-gamma, the nitrite-inducing activity was found to be heat labile, with over 90% of the activity lost within 5 minutes of h eating, These results show that chicken T cells produce IFN-gamma.