title: IL-2, IL-6, and IFN-gamma have distinct effects on the IL-4 plus PMA-induced proliferation of thymocyte subpopulations.
abstract: We have previously reported complex effects of cytokine-containing T cell supernatants on the interleukin (IL)4 plus phorbol 12-myristate 13-acetate (PMA)-induced proliferative response of murine thymocytes. Here we show that recombinant murine IL-2, IL-6, and IFN-gamma each differentially regulate the IL-4/PMA-driven growth of thymocyte subpopulations. Thymocytes fractionated into four subpopulations on the basis of CD4 and CD8 expression were stimulated to proliferate by IL-4/PMA. Interferon-gamma (IFN-gamma) caused almost complete inhibition of the CD4+/CD8- response but had no measurable effect on the growth of CD4-/CD8+ or CD4-/CD8- populations. This inhibitory effect was also observed on splenic CD4+/CD8- T cells. In contrast, IL-6 strongly enhanced the proliferative response of CD4+/CD8- thymocytes, but showed no effect on peripheral CD4+/CD8- T cells, suggesting that IL-6 may be an important regulator of growth in the thymus. IL-2 also enhanced the proliferation of both CD4-/CD8+ and CD4-/CD8- thymocytes to IL-4 and PMA. To test whether the IL-4/PMA stimulus provided all the signals required to initiate growth in each subpopulation, we titrated cell number and examined the relationship between cell dose and cell response. Growth of CD8+/CD4- cells was cell density independent, indicating that IL-4/PMA is sufficient stimulus to induce growth of these cells. In contrast, growth of CD4-/CD8- and CD4+/CD8- cells is cell density dependent, suggesting a requirement for another signal provided by the cells themselves. These observations suggest that more signals remain to be identified in this thymocyte growth system.
authors.affiliation: DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, California 94304-1104.
authors.forename: P D
authors.initials: PD
authors.lastname: Hodgkin
authors.forename: J
authors.initials: J
authors.lastname: Cupp
authors.forename: A
authors.initials: A
authors.lastname: Zlotnik
authors.forename: M
authors.initials: M
authors.lastname: Howard
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens; D002478:Cells, Cultured; D005260:Female; D007371:Interferon-gamma / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology*; D015847:Interleukin-4 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D016827:CD8 Antigens; D007376:Interleukin-2; D015850:Interleukin-6; D015847:Interleukin-4; D007371:Interferon-gamma; D013755:Tetradecanoylphorbol Acetate