Growth Hormone Receptors and Insulin-like Growth Factor I Receptors on Human Peripheral Blood Cells

Abstract

Growth hormone (GH) and insulin-like growth factor I (IGF-I) may be able to modulate some functions of the immune system. In this study, we examined the expression of the receptors for GH and IGF-I on human peripheral blood cells in physiological and pathological conditions.By using two-colour analysis on flow cytometry with a biotinavidin system, there was a specific GH binding site on human peripheral lymphocytes. GH-binding was more prominent on CD20+ (=B cells) than on CD2+ (=T cells), although GH receptor messenger ribonucleic acid (mRNA) could be detected in the T cells as well as in the B cells. There was no age-dependency of GH-binding on the CD20 cells, and there was no relationship between GH-binding and serum GHbinding protein activities, which reflect the tissue levels of GH receptors.We detected αIR3, anti IGF-I receptor antibody, bindings and IGF-I receptor mRNA expression in peripheral blood cells. Based on two-colour analysis, there were relatively higher bindings of αIR3 on CD4+ and CD16+ cells, intermediate bindings on CD8+ cells and weak bindings on CD20+ cells. In cord blood cells, αIR3 bindings and IGF-I receptor mRNA were higher than in adult cells. In GH-deficient patients, αIR3 bindings were higher than in control subjects, and reverted to normal after GH therapy.These results suggest that 1) GH and IGF-I may have hormonal effects on the immune system, 2) GH receptors on lymphocytes dose not correlate with the tissue levels of GH receptors, and 3) the cellular levels of IGF-I receptors may be inversely related to the ambient IGF-I concentrations.