Limited effects of placental and pituitary growth hormone on cytokine expression in vitro

The hypothesis that growth hormone (GH) can affect immune responses in man has been evaluated by monitoring cytokine expression in cultures from perip heral blood mononuclear cells, by enzyme-linked immunosorbent assay (ELISA) and ribonuclease protection assay, and in tonsillar cells by ELISA. In add ition to pituitary GH (GH-N), the placental form (GH-V), differing from pit uitary GH by 13 amino acids has also been tested. Only few effects reached statistical significance and were in no case greater than 15%. Pituitary GH slightly reduced IL-5 production and stimulated IFN-gamma production. The latter effect was also observed with prolactin and could thus be induced th rough the prolactin receptor. It is proposed that GH has no strong effects on the parameters investigated, possibly as a result of redundancy in the c ytokine network. Alternatively, effects on leukocytes are mediated by other tissues such as the liver or are clear only in response to stronger challe nges.