Effect of triiodothyronine and in vitro growth hormone on avian interleukin-2

Abstract One-day-old chickens were treated with varying levels of triiodothyronine (T 3 ) added to the diet. At 28 days of age, the IL-2-like activity in the splenocyte culture supernatants were assessed. The lowest dose of T 3 (0.1 ppm) enhanced IL-2-like activity while the highest dose (1.0 ppm) was significantly suppressive. The intermediate dose elicited varying effects. Recombinant chicken growth hormone (rcGH) was added to some cultures 24 h prior to IL-2 assay. In vitro rcGH significantly depressed the IL-2-like activity of splenocytes from animals given the low T 3 diet. The addition of varying concentrations of T 3 in vitro to splenocytes from non-T 3 -supplemented chickens had no effect on the IL-2-like activity. These results indicate that in vivo supplementation of low dietary T 3 but not in vitro T 3 is effective in enhancing avian IL-2-like activity. The addition of rcGH in vitro can modify this response.