Effect of elevated growth hormone concentrations on the phenotype and functions of human lymphocytes and natural...

Over the past decades, strong evidence has accumulated that growth hormone (GH) has immunostimulatory properties. Therefore, an investigation was conducted on 10 acromegalic patients and 9 age- and sex-matched healthy controls to determine whether plasma GH concentrations correlate with changes in several immune parameters, including serum concentrations of immunoglobulins, lymphocyte subsets, lymphocyte transformation with phytohemagglutinin (PHA), natural killer (NK) cell activity as well as phagocytic and metabolic burst activity. While NK cell activity, serum concentrations of immunoglobulins (IgG, IgM, IgA) and metabolic burst activity were within the normal range in both groups, a significantly enhanced phagocytic activity was observed in the acromegalic patients. Surface markers on T lymphocytes (CD3, CD4, CD8), B lymphocytes (CD19) and NK cells (CD16/56) were normal in both groups; however, in the acromegalic subjects, CD4+ and CD8+ cells showed a significant higher expression of transferrin receptors (CD71), indicating enhanced T-cell activity. The lymphocyte transformation response to PHA at the highest concentration tested showed a tendency to be elevated in acromegalics; however, the difference failed to be significant. Long-lasting and pronounced elevation of GH in acromegaly induces significantly enhanced phagocytic activity, but only negligible changes in most patients in lymphocyte phenotype and in the lymphocyte response to PHA.