AN EXAMINATION OF THE IMMUNE-SYSTEM OF THE DUCK (ANAS-PLATYRHYNCHOS) FOR FACTORS RESEMBLING SOME DEFINED MAMMALIAN CYTOKINES

Duck lymphoblasts generated by phytohaemagglutinin (PHA) did not respo nd to recombinant or Jurkat cell line human interleukin (IL)-2 or poss ess surface antigens resembling mammalian IL-2 receptors or IL-1beta. Supernatant fluids from normal and PHA-stimulated duck lymphocyte cult ures, and normal and lipopolysaccharide (LPS)-stimulated monocytes, ga ve negative results in a range of assays for biological activity and i mmunochemical presence of factors resembling mammalian IL-1 and IL-2. However, supernatant fluids from LPS-stimulated duck monocytes contain ed IL-6-like activity (up to 35 units/mL) assessed on the 7TD-1 murine cell line. We were unable to demonstrate mRNA that would hybridize to cDNA probes for human IL-1beta, IL-6, and tumour necrosis factor (TNF ) in extracts of blood and lymphoid organs from normal and antigen-sti mulated ducks. Because homologous serum or plasma is essential for duc k lymphocytes and macrophages to respond to mitogens in vitro, we aske d whether this growth-factor-like activity might be caused by substanc es resembling mammalian cytokines. Serum and plasma were examined for activity consistent with IL-1 and IL-6 on mammalian target cells. None was detected. Instead, both serum and plasma contained inhibitors of human IL-1beta and IL-6, detected at dilutions up to 1:100. Inhibition by serum was heat (56-degrees-C, 30 min) labile but inhibition by pla sma was heat stable. The identities and biological functions of these inhibitors remain to be defined.