title: Insulin-like growth factor I is an independent coregulatory modulator of natural killer (NK) cell activity.
abstract: We aimed to investigate the natural killer (NK) cell activity in hGH-deficient adults and to analyze the effect of insulin-like growth factor (IGF)-I in vivo and in vitro on NK cell activity. NK cell activity was measured in a 4-h nonisotopic assay with europium-labeled and cryopreserved K-562 cells. NK-cell numbers were measured after incubation with murine monoclonal CD3 and CD16 antibodies by flow cytometry analysis. In a cross-sectional study, the basal and interferon-beta (IFN-beta) stimulated (1000 IU/ml) NK cell activity of 15 hGH-deficient patients and 15 age- and sex-matched controls was measured. The percentages and absolute numbers of CD3-/16+ NK-cells were not significantly different in the patient vs. control group. The basal and IFN-beta stimulated NK cell activity however was significantly decreased in the patient vs. control group at all effector/target (E/T) cell ratios from 12.5-100 (e.g. 17 +/- 3 vs. 28 +/- 3% lysis without IFN-beta, P < 0.05, and 42 +/- 4 vs. 57 +/- 4% lysis with IFN-beta, P < 0.05; both at E/T 50). IGF-I levels of patients and controls showed a significant positive correlation with NK cell activity (r = 0.37; P < 0.05). In an IGF-I in vitro study (IGF-I in vitro 250-1250 microg/L), the basal and IFN-beta stimulated NK cell activity of 13 hGH-deficient patients and of 18 normal subjects was significantly enhanced by IGF-I in vitro (e.g. GH-deficient patients: 9 +/- 2 vs. 10 +/- 2% lysis without IFN-beta, P < 0.05 and 25 +/- 4 vs. 30 +/- 4% lysis with IFN-beta, P < 0.005; and normal subjects: 15 +/- 3 vs. 23 +/- 3% lysis without IFN-beta, P < 0.001 and 35 +/- 4 vs. 44 +/- 5% lysis with IFN-beta, P < 0.001; both at IGF-I 500 microg/L). In summary, in our cross-sectional study, adult GH-deficient patients showed a significantly lower basal and IFN-beta stimulated NK cell activity than matched controls, despite equal NK cell numbers. IGF-I levels of patients and controls showed a weak positive correlation with NK cell activity. In an in vitro study, IGF-I significantly enhanced basal and IFN-beta stimulated NK cell activity of hGH-deficient patients and also of normal subjects. The decreased NK cell activity in GH-deficient patients may be caused at least in part by low serum IGF-I levels. IGF-I appears to be an independent coregulatory modulator of NK cell activity.
authors.affiliation: Medizinische Klinik, Klinikum Innenstadt, Ludwig-Maximilians-Universitat Munchen, Munich, Germany.
authors.forename: C J
authors.initials: CJ
authors.lastname: Auernhammer
authors.forename: H
authors.initials: H
authors.lastname: Feldmeier
authors.forename: R
authors.initials: R
authors.lastname: Nass
authors.forename: K
authors.initials: K
authors.lastname: Pachmann
authors.forename: C J
authors.initials: CJ
authors.lastname: Strasburger
mesh_terms: D000328:Adult; D002452:Cell Count / Q000187:drug effects; D003430:Cross-Sectional Studies; D005260:Female; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology / Q000502:physiology*; D016899:Interferon-beta / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009994:Osmolar Concentration; D011994:Recombinant Proteins; D012016:Reference Values
chemical_list: D011994:Recombinant Proteins; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D016899:Interferon-beta