IDENTIFICATION OF TRANSFORMING GROWTH-FACTOR-BETA AND INTERLEUKIN-6 IN CHICKEN ASCITES-FLUID

Ascites fluids from chickens were analyzed for the occurrence of trans forming growth factor-beta (TGF-beta) and interleukin-6 (Il-6) using t he mink lung epithelial cell inhibition and B9 hybridoma proliferation assays, respectively. Both of these cytokines were significantly elev ated in ascites fluids (TGF-beta, 0.129 +/- 0.017 ng/mg protein; Il-6, 0.054 +/- 0.011 ng/mg protein) relative to serum (TGF-beta, 0.005 +/- 0.003 ng/mg protein; Il-6, <0.002 ng/mg protein) derived from the sam e individual birds. TGF-beta occurred in a latent form and required ac tivation by heat or acid (heat, 100%; non-activated, 5.2 +/- 1.1%; aci d activated, 89.5 +/- 12.3%). Heat treatment destroyed Il-6 activity. Both TGF-beta and Il-6 activities could be neutralized by antibodies d irected against the recombinant human counterpart of these cytokines. Increasing dilutions of ascites fluid caused proportionate decreases i n cytokine activities. Il-6 activity was further characterized by gel filtration using high-pressure liquid chromatography, which yielded a peak of biological activity corresponding to an approximate molecular weight of 35,000. These data suggest that ascites fluid may be an inte resting biological model and source for studying avian cytokines and t heir physiological relevance.