Stimulatory effects of immunoreactive growth hormone on proliferation of a human lymphocyte cell line

Previous studies have indicated the secretion of a growth hormone-like molecule by the lymphocyte T-cell line, H9. We examined the autocrine growth-promoting effects of this T-cell derived factor. H9 conditioned medium stimulates proliferation of H9 cells themselves in a dose-dependent fashion. This growth stimulating effect could be blocked by anti-human growth hormone antiserum, but could not be simulated by addition of growth hormone only or interleukin 2 only, or a combination of both. Dexamethasone inhibited H9 growth in low nutrient culture conditions and seemed to somewhat offset the growth promoting effect of the hGH-like molecule. However, the exact role played by dexamethasone in H9 cell growth and death, as well as the exact mechanism by which the hGH-like molecule exerted its growth-promoting action, remain to be elucidated.