title: Type I insulin-like growth factor receptor expression in different developmental stages of human thymocytes.
abstract: Insulin-like growth factor-I (IGF-I) has been implicated in playing a regulatory role in T cell development and in T cell function. We demonstrate the presence of type I IGF receptors on human thymocytes using radioligand binding assays and flowcytometric analysis. The relative potencies of IGF-I, IGF-II and insulin for competition with 125I- IGF-I indicate the presence of type I IGF receptors. Scatchard analysis revealed that the average number of receptors per thymocyte is 257 +/- 28 with a Kd of 0.12 +/- 0.01. With multicolour flowcytometry using a type I IGF receptor specific monoclonal antibody (alpha IR3), we show that CD4-CD8- cells express 3-4 times more receptors per cell as compared with CD4+CD8+, CD4+CD8- and CD4-CD8+ cells. IGF-I directly stimulated DNA synthesis of thymocytes and potentiated DNA synthesis in mitogen-activated thymocytes. These results indicate that IGF-I can influence T cell development in humans at the level of the thymus.
mesh_terms: D001667:Binding, Competitive; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D011869:Radioligand Assay; D017526:Receptor, IGF Type 1 / Q000032:analysis* / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism* / Q000502:physiology; D013950:Thymus Gland / Q000378:metabolism
chemical_list: D007328:Insulin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA; D017526:Receptor, IGF Type 1