Abstract. These data describe the effects of purified preparations of several growth factors on thymidine incorporation into phyto-haemagglutinin-activated (PHA) human lymphocytes. The somatomedins selected for this study included human somatomedins A and C, insulin-like growth factors (IFG1) and IGF2) and multiplication stimulating activity (MSA). Assays were carried out with and without serum. Complementary assays were performed with a low-molecular serum ultrafiltrate added to somatomedin C and to MSA. We found that all the peptides tested, except MSA, stimulated thymidine incorporation into PHA-activated lymphocytes in a dosedependent manner, even though different doses were required to obtain a response. The data reported point out the multiplicity and the interrelationships of the serum factors involved in the stimulation of human cells growth.
Abstract. Cultures of human blood peripheral lymphocytes were performed in the presence or absence of human growth hormone, and also of phytohemagglutinin and normal human serum 10%. After incubation for 48 h, the supernatants were tested for their ability to promote the uptake of [3H]thymidine into lectin-activated lymphocytes. Supernatants from lymphocyte-free control samples, treated in the same manner, were assayed under the same experimental conditions. Variance analysis of the different dose-response relationships was performed. The results of these in vitro experiments confirm that physiological levels of GH inhibit the lectin-induced lymphoproliferation and that lymphocytes secrete an 'activity' able to stimulate the incorporation of [3H]thymidine into lectin activated lymphocytes. Furthermore we show that: 1) Secretion of this lymphocyte-stimulating activity is increased by physiological levels of GH; 2) This lymphocytic secretion is not radioimmunoassayable IGF-I; 3) Using fast protein liquid chromatography (FPLC), this activity appears in fractions with various molecular weights.
Interleukin-1α (IL-1α) and interleukin-2 (IL-2) levels were measured by radioimmunoassay in samples of conditioned medium from mononuclear cells taken from 20 normal subjects (14 adults ranging in age from 20 to 45 years and 6 children ranging in age from 3 to 11 years) and from 49 children with growth delay. Cultures were performed with 106 cells/ml in medium containing 1 % normal human serum and 4.8 g/l phytohemagglutinin M. The incubation was performed for 48 h in an atmosphere containing 5 % CO2. In normal subjects, the production of IL-lα was 38.5 ± 9.8 fmol/ml of conditioned medium (mean ± SEM) in 14 adults and 41.6 ± 3.0 fmol/ml in 6 children. The production of IL-2 was 46.9 ± 6.5 and 57.3 ± 10.5 fmol/ml, respectively. In the 16 patients with growth hormone (GH) deficiency studied before treatment, the production of ILs was significantly decreased in relation to the degree of deficiency. We observed a positive correlation between the produciton of IL-lα and the values of insulin-like growth factor I but not with serum GH values. IL-lα production was normalized after 15 days of substitutive GH therapy and IL-2 was normalized after 3 months of therapy. In 10 other patients with GH deficiency (4 with total and 6 with partial isolated GH deficiency) studied after long-term GH treatment (5 months or more), the mean of IL production was not significantly different from that of GH-deficient children treated for 3 months. In the 23 patients with constitutional delay of growth, we observed also a significant decrease in ILs compared to the control. No correlation was found between IL production and bone age ranging from 3 to 10 years. We conclude that GH is required for IL production.
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