Modulation of lymphoproliferation by human growth hormone

This study was designed to investigate the capacity of human growth hormone (hGH) to induce proliferation of human peripheral blood lymphocytes (PBL) and its effect on lectin-induced lymphoproliferation, as measured by [3H]-thymidine (3H-TdR) incorporation into lymphocyte DNA. We observed that hGH itself induced lymphoproliferation. Maximal responses were reached with 50 ng/ml after 4 days and 25 ng/ml after 7 days. Anti-hGH-antiserum completely blocked the stimulatory capacity of hGH. Further evidence for the specificity of the effect was obtained by the finding that no other hormone present in the hGH preparation produced any effect on lymphocyte cultures. In contrast to its stimulatory capacity, hGH reduced the proliferative response of PBL to phytohaemagglutinin (PHA). This effect was also neutralized by anti-hgH-antiserum. These results show a direct stimulatory effect of hGH on PBL and a regulatory effect of the hormone on lectin-induced lymphoproliferation.