Growth hormone stimulates production of interferon-gamma by human peripheral mononuclear cells

There is substantial evidence for interactions between the immune and endocrine systems at different levels. In the present study we investigated whether human growth hormone (hGH) could stimulate proliferation of interferon-γ-secreting cells (IFN-γ-SC), and production of IFN-γ. Human peripheral blood mononuclear cells (PBMC) taken from 15 normal subjects were incubated with varying doses (200,400, 600 and 800 ng/ml) of recombinant hGH. Samples of cells were also incubated with PBS buffer (without hGH) to serve as controls. Effects of hGH were studied by enumerating IFN-γ-SC and by measuring the concentration of IFN-γ using an Immunospot assay and an enzyme-linked immunosorbent assay, respectively. The results showed that hGH significantly increased both the number of IFN-γ-SC and the concentration of IFN-γ in a dose-dependent manner. The maximum effects were obtained in the presence of (400 ng/ml) hGH (15 ± 5 IFN-γ-SC/10⁶ PBMC and 300 ± 55 U/ml IFN-γ) compared to controls (4 ± 2 IFN-γ-SC/10⁶ PBMC and 50 ± 10 U/ml IFN-γ). The results of the present study suggest that hGH might influence the immune system by stimulating the proliferation of IFN-γ-SC and the production of IFN-γ.