EFFECT OF ELEVATED GROWTH-HORMONE CONCENTRATIONS ON THE PHENOTYPE ANDFUNCTIONS OF HUMAN-LYMPHOCYTES AND NATURAL-KILLER-CELLS

Over the past decades, strong evidence has accumulated that growth hor mone (GH) has immunostimulatory properties. Therefore, an investigatio n was conducted on 10 acromegalic patients and 9 age- and sex-matched healthy controls to determine whether plasma GH concentrations correla te with changes in several immune parameters, including serum concentr ations of immunoglobulins, lymphocyte subsets, lymphocyte transformati on with phytohemagglutinin (PHA), natural killer (NK) cell activity as well as phagocytic and metabolic burst activity. While NK cell activi ty, serum concentrations of immunoglobulins (IgG, IgM, IgA) and metabo lic burst activity were within the normal range in both groups, a sign ificantly enhanced phagocytic activity was observed in the acromegalic patients. Surface markers on T lymphocytes (CD3, CD4, CD8), B lymphoc ytes (CD19) and NK cells (CD 16/56) were normal in both groups; howeve r, in the acromegalic subjects, CD4+ and CD8+ cells showed a significa nt higher expression of transferrin receptors (CD71), indicating enhan ced T-cell activity. The lymphocyte transformation response to PHA at the highest concentration tested showed a tendency to be elevated in a cromegalics; however, the difference failed to be significant. Long-la sting and pronounced elevation of GH in acromegaly induces significant ly enhanced phagocytic activity, but only negligible changes in most p atients in lymphocyte phenotype and in the lymphocyte response to PHA.