Interferon-γ upregulates 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

Abstract

The human interleukin-3 (IL-3) receptor is constitutively expressed on certain hematopoietic cells where it mediates proliferation and differentiation, or functional activation. We have recently found that human umbilical vein endothelial cells (HUVECs) also express IL-3 receptors and that the expression is enhanced by stimulation with the monokine tumor necrosis factor α. In this report we show that the lymphokine interferon γ(IFNγ) is a powerful stimulator of the IL-3 receptor of HUVECs and that the combination of IL-3 and IFNγ has a synergistic effect on major histocompatibility complex (MHC) class II expression and on the production of the early-acting hematopoietic cytokines IL-6 and granulocyte colony-stimulating factor (G-CSF). IFNγ caused a time-and dose-dependent up-regulation of mRNA for both the α and β chains of the IL-3 receptor, with maximal effects occuring 12 to 24 hours after stimulation with IFNγ at 100 U/ mL. Induction of mRNA correlated with protein expression on the cell surface, as judged by monoclonal antibody staining of both receptor chains and by the ability of HUVEC to specifically bind 125I-labeled IL-3 (125I-IL-3). Scatchard analysis of HUVECs stimulated with IFNγ at 100 U/mL for 24 hours showed ≈6,300 IL-3 receptors per cell that were of a high affinity class (dissociation constant [kd] = 500 pmol/ L) only. The addition of IL-3 to IFNγ-treated HUVECs strongly enhanced the expression of MHC class II antigen. Importantly, IFNγ 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 of G-CSF and IL-6 protein in HUVEC supernatants. In contrast, IFNγ and IL-3 did not stimulate granulocyte-macrophage colony-stimulating factor (GM-CSF) or IL-8 production in HUVECs. These results show that IFNγ is a strong stimulator of IL-3 receptor expression in HUVECs and suggest that in vivo T-cell activation, causing the concomitant production of IFNγ and IL-3, may lead to enhanced endothelial MHC class II expression and to the selective production of early-acting hematopoietic cytokines. Thus, IL-3 could influence immunity and hematopoiesis by acting not only on hematopoietic cells, but also on vascular endothelium. © 1995 by The American Society of Hematology.