INTERFERON-GAMMA UP-REGULATES INTERLEUKIN-3 (IL-3) RECEPTOR EXPRESSION IN HUMAN ENDOTHELIAL-CELLS AND SYNERGIZES WITH IL-3 IN STIMULATING MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II EXPRESSION AND CYTOKINE PRODUCTION

The human interleukin-3 (IL-3) receptor is constitutively expressed on certain hematopoietic cells where it mediates proliferation and diffe rentiation, or functional activation, We have recently found that huma n umbilical vein endothelial cells (HUVECs) also express IL-3 receptor s and that the expression is enhanced by stimulation with the monokine tumor necrosis factor alpha. In this report we show that the lymphoki ne interferon gamma (IFN gamma) is a powerful stimulator of the IL-3 r eceptor of HUVECs and that the combination of IL-3 and IFN gamma has a synergistic effect on major histocompatibility complex (MHC) class II expression and on the production of the early-acting hematopoietic cy tokines IL-6 and granulocyte colony-stimulating factor (G-CSF). IFN ga mma caused a time- and dose-dependent up-regulation of mRNA for both t he alpha and beta chains of the IL-3 receptor, with maximal effects oc curing 12 to 24 hours after stimulation with IFN gamma at 100 U/mL. In duction of mRNA correlated with protein expression on the cell surface , as judged by monoclonal antibody staining of both receptor chains an d by the ability of HUVEC to specifically bind I-125-labeled IL-3 (I-1 25-IL-3), Scatchard analysis of HUVECs stimulated with IFN gamma at 10 0 U/mL for 24 hours showed approximate to 6,300 IL-3 receptors per cel l that were of a high affinity class (dissociation constant [kd] = 500 pmol/L) only. The addition of IL-3 to IFN gamma-treated HUVECs strong ly enhanced the expression of MHC class II antigen, Importantly, IFN g amma and IL-3 also exhibited a synergistic effect in the induction of the mRNA for G-CSF and IL-6. This was reflected in increased amounts o f G-CSF and IL-6 protein in HUVEC supernatants. In contrast, IFN gamma and IL-3 did not stimulate granulocyte-macrophage colony-stimulating factor (GMCSF) or IL-8 production in HUVECs. These results show that I FN gamma is a strong stimulator of IL-3 receptor expression in HUVECs and suggest that in vivo T-cell activation, causing the concomitant pr oduction of IFN gamma and IL-3, may lead to enhanced endothelial MHC c lass II expression and to the selective production of early-acting hem atopoietic cytokines. Thus, IL-3 could influence immunity and hematopo iesis by acting not only on hematopoietic cells, but also on vascular endothelium. (C) 1995 by The American Society of Hematology.