GROWTH-HORMONE INHIBITS NORMAL B-CELL DIFFERENTIATION AND NEUTROPHILSCHEMOTAXIS IN-VITRO

In acromegalic patients we have previously described a low ability of B-lymphocytes to differentiate into plasma cells under PWM stimulation , and a decreased chemotaxis of polymorphonuclear leukocytes (PMN) tow ards N-formylmethionylphenilalanine (FMP). In this study we examined t he effect of exogenous GH over these immune functions in normal cells. PMN were purified by dextran sedimentation, incubated with recombinan t human GH (0 to 20 ng/ml) and subjected to stimulation with FMP. PBMC were cultured with or without PWM, in the presence of GH (between 0 a nd 100 ng/ml). Plasma cells were determined as hemolysis plaque formin g cells and also by immunofluorescence. GH, in a dose-dependent way, d ecreased directed migration of PMN (5 ng/ml: 1.787 +/- 148 mu m; 10 ng /ml: 1.581 +/- 221 mu m; 20 ng/ml: 1.569 +/- 149 mu m, all as mean +/- S.E.M.), when compared to similar values of untreated PMN (0 ng/ml 2. 085 +/- 139 mu m). GH treatment did not modify spontaneous migration. Net migration showed the same pattern as directed migration. GH decrea sed dose-dependently the PWM-driven differentiation of B-lymphocytes i nto plasma cells to 60% of the basal level. Although not significantly , GH tended to increase spontaneous B-cell differentiation. These resu lts could account for the already described defect in B-cell different iation and PWN chemotaxis in acromegaly, emphasizing the relationship between the endocrine and immune systems.