Augmentation of natural cell-mediated cytotoxic activity by supernatant from in vitro mitogen-stimulated, in vivo hormone-treated lymphocytes in immature male (K strain) chickens.

Newly hatched White Leghorn male chicks were used in this study. Triiodothyronine (T3; 0.1 or 1 ppm) and Thyrotropin Releasing Hormone (TRH; 1 or 5 ppm) were added to the feed for an 8-week period starting at hatch. A fifth group received the unsupplemented diet and served as controls. Peripheral blood lymphocytes from each treatment group were cultured in vitro with or without different mitogens (PHA, Con-A, or LPS), and the culture supernatants were tested for the presence of lymphokines (LK). The natural cell-mediated cytotoxicity (NCMC) assay was carried out with or without supernatant using the standard chromium (Cr51) release assay. Control untreated chicks were used as donors for effector cells and the P815 mouse mastocytoma was used as a target. Supernatant from in vivo 1 ppm T3- or 5 ppm TRH-treated lymphocytes significantly suppressed NCMC (or cells mediating NCMC, e.g., NK cells). However, supernatant from 1 ppm T3-treated, PHA-stimulated lymphocytes significantly enhanced NK cells cytotoxicity, while supernatant from 5 ppm TRH-treated lymphocytes with PHA stimulation tended to suppress cytotoxicity. These results provide evidence supporting a regulatory role of the hypothalamo-pituitary thyroid axis on lymphokine (LK) production. The results also suggest that these hormones act on different subpopulation of lymphocytes, and therefore, the mediators released by them.