title: Human thymocytes do not respond to interleukin-2 after removal of mature "bright" CD5 positive cells.
abstract: Interleukin-2 receptors (IL-2R) are expressed on minor populations of immature and mature human thymocytes. These studies were designed to determine if immature T cells could respond to the mitogen phytohemagglutinin (PHA-P) plus IL-2 in vitro by increasing the expression of IL-2R and by proliferation. Using monoclonal antibodies to CD5 and magnetic immunobeads we were able to remove all mature, "bright" CD5+ cells from nylon wool-purified thymocytes and to obtain less mature cells which consisted almost completely of cells with the CD4+CD8+ phenotype. These immature cells were mostly "dim" CD5+ and less than 5% CD5- and a small percentage expressed the IL-2R. After culture in serum-free medium with PHA-P, these cells showed only a slight increase in the percentage of IL-2R+ cells and the addition of IL-2 did not increase the percentage of IL-2R+ cells and no proliferation was observed. Unseparated, nylon wool-purified thymocytes contained 14% bright CD5+ cells. These bright CD5+ cells had a mature phenotype of CD4+CD8- (52%) and CD4-CD8+ (27%) cells. A small percentage of these cells were IL-2R+. These bright CD5+IL-2R+ cells were predominantly mature CD4+CD8- cells as measured by three-color flow cytometry. After culture with PHA-P and IL-2, the percentage of IL-2R+ cells increased and they were now found not only on CD4+CD8- but also on CD4-CD8+ and on CD4+CD8+ cells. IL-2 plus PHA-P increased proliferation of these cells as compared to those cultured in medium with PHA-P without IL-2. Thus, we show that human immature thymocytes in contrast to mature thymocytes are not responsive to IL-2 as measured by a lack of IL-2R expression and proliferation. These data indicate that mature thymocytes can express a functional high affinity receptor for IL-2 and suggest that immature thymocytes may not possess a (functional) p75 chain of the IL-2R.
authors: Department of Microbiology, UCLA School of Medicine 90024.
authors: Y
authors: Y
authors: Ueno
authors: E F
authors: EF
authors: Hays
authors: L
authors: L
authors: Hultin
authors: C H
authors: CH
authors: Uittenbogaart
mesh_terms: D015703:Antigens, CD / Q000032:analysis*; D000943:Antigens, Differentiation / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens / Q000032:analysis; D018956:CD5 Antigens; D016827:CD8 Antigens; D002454:Cell Differentiation; D002469:Cell Separation; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology*; D008213:Lymphocyte Activation; D010835:Phytohemagglutinins / Q000494:pharmacology; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D018956:CD5 Antigens; D016827:CD8 Antigens; D007376:Interleukin-2; D010835:Phytohemagglutinins; D015375:Receptors, Interleukin-2